My Home Solar Panels

Frequently Asked Questions

1. QUESTION:
   Hot water solar collector tube work or not in UK weather?
   Hot water solar collector tube work or not in UK weather?
   Could you give me some advice please. I want to know about the solar collector evacuated tube. Are they strong enough? I heard that some of this tube are explode or break when it get very hot. I want to know how reliable they are. Are they work in UK weather or not or is it a waste of money, because most of the time is cloudy. If it does work how many tube require to heat 210 litres water cylinder

   • ANSWER:
     this is what i do for a living.

     Yes evacuated tubes etc WILL work,BUT flat plat panels are just as good these days. The problem with most tube design is that they are self limiting at a relatively low temp, so in the summer they will "switch off" once they reach a certain temp, where flat plates will keep transferring the energy to your water until it reaches a programmed cut off which is quite high but safe.

     There was a few cases of tubes exploding when they got too hot, not heard about that for a few years now though, problem seems to be fixed. Tubes only last (usually) 10 years, where flat plates will last 25+.

     2 flat plates will be good for 210 L AND won't need replaced!

2. QUESTION:
   Can I use liquid boiler sealer or radiator sealer to seal a small leak in my solar collector?
   I have a small leak on the inside of my solar hot water collector. Is there something I could mix with the water to seal the leak, since you cannot open the collector? I was thinking of a liquid boiler sealer or radiator sealer. It uses copper pipes and reaches temps of about 200 degrees max.

   • ANSWER:
     You run the risk of clogging valves, damaging sensors and coating the inside of the pipes and reducing their efficiency. Even if a leak is sealed by an additive, no manufacturer will guarantee that such a seal will last. Repairing or replacing the leaky pipe or fitting is the best cure. The collector may be sealed so it is not supposed to be opened, but there must be some way to get into it to make repairs and then reseal it. You might need to have someone with a vacuum pump evacuate the panel after it is opened and the pipe repaired.

3. QUESTION:
   A hot-water heater is operated by solar power. If the solar collector has an area of 6.0 m2 and the power deli?
   A hot-water heater is operated by solar power. If the solar collector has an area of 6.0 m2 and the power delivered by sunlight is 550 W/m2, how long will it take to increase the temperature of 1 m3 of water from 23°C to 61°C?

   • ANSWER:
     Rate of heat supply = 550 J/s x 6.0m² = 3300 J/s

     Heat energy required H = m.s.∆θ
     H = (1000kg)(4200 J/kg.ºC)(38ºC) = 1.60^8 J

     t = 1.60^8 J / 3300 J/s .. .. ►t = 4.84^4 s .. (13.4 hr)

4. QUESTION:
   will hot water solar panel collectors work in outer space?
   closed loop type system,and would a heat exchanger type system work as well in space as on the planet earth

   • ANSWER:
     yes, although the system would have to be insulated so the water wouldn't freeze, another liquid such as liquid nitrogen would be more efficient and cheaper to maintain in space

5. QUESTION:
   Solar hot water heater with seperated panels and a vertical tank system.?
   In a solar hot water system where the solar panels are placed on the roof but the collector is placed on the ground, how much energy is required to pump the heated water from the panels on the roof to the collector on the floor?

   • ANSWER:
     Depending on the distance the collectors are from the tank, and the size of the pipes, a Taco 006 is often used. It is a 1/40th HP pump and draws 60W. http://www.altestore.com/store/Solar-Water-Heaters/Solar-Hot-Water-Circulator-Pumps/Ac-Pumps/Taco-140-HP-Bronze-Pump-34-115-VAC-006-B4/p122/

     An alternative is to use a DC powered pump, like the Laing D5, and have it run off a 10 - 30W PV panel. http://www.altestore.com/store/Solar-Water-Heaters/Solar-Hot-Water-Circulator-Pumps/Dc-Pumps/Laing-D5720B-PV-Circulating-Pump-sweated/p6065/

6. QUESTION:
   A house uses solar energy to produce hot water..?
   Fig 4.1 of question four in the link below shows solar equipment placed on top of a house that uses solar energy to produce hot water.

   1. explain why the solar collector has a black base.
   2. State and explain why the hot water in the solar collector travels to the hot water tank.
   3. The figure does not show any insulation.
   a. Explain the importance of insulating the hot-water tank.
   b. Explain how the hot water tank is insulated.

   http://www.dpe.edu.mv/dpe/downloads/data/pp/862febd35277bd87708fadc8cb974165.pdf

   • ANSWER:
     1.It is black because the color black absorbs all the light photons. If it were white, it would reflect all the photons away and won't heat the water much.
     2.The water travels to the tanks because warm water is less dense than cold water and rises. This is not true with ice tho. Ice is less dense than warm water but it is in another phase. Warm water is less dense than cool water only if water is in liquid phase.
     3.a)Water may be a good heat sink(stores heat well) heat will escape the tank if the tank is not properly insulated. As heat escapes the water in the tank cools therefore making the solar energy less efficient.
     b)Possible ways of insulating the tank is to have the tank made out of some bad conducting medal(insulator) I can't think of any bad conducting medal but copper, silver, tin, aluminum are very conductive and would make bad insulators. You don't even need to have the tank made out of medal. Anything that is hard and durable with low conductance will do. Like a thermostat. The inner part of the thermos is made out of a low conducting medal. Middle layer is usually plastic or Styrofoam because those are good insulators.

     Hope this is clear and helpful.

7. QUESTION:
   Can I create a cheap but effective solar hot water heater for bathing using my south-facing bathroom window?
   I moved into an older brick bungalow recently. We have just one bathroom, with a south-facing window (original glass) that's about 2-1/2' wide by 3-1/2'. The window is above the toilet, which sits right next to the soaking tub. I've never attempted to construct anything more complex than a small cardboard box solar cooker, and I don't have much to spend on this project. But I'd like to try and construct a simple, insulated collector/holding tank in the window, which can extend beyond the window area itself in all directions only a couple of feet. But I do also have a wide linen closet on the other side of the toliet that has extra space for storage, if needed. I just want to heat enough water for daily bathing for a family of three. It could be as rudimentary as something I fill with water from a hose, and then have a way for it to flow down into the tub once heated. Any ideas, or is this something I need a more high-tech solution or more space for?

   • ANSWER:
     buy a 2 panel solar thermal system and be done with it. you get tax credits and a much more efficient system (95%). go to appalachianenergy.com. we have 60 systems ready to ship as i type.

8. QUESTION:
   Would you agree with a bill that would mandate consumer hot water tanks be solar ready-heat exchanger inside?
   To me this is one area that this generation of shower takers, clothing washers, and tea drinkers could become a little more aware about. Yes, it would be extremely simple,upon manufacturing, to install inside currently made gas and electric hot water tanks a coil of non corrosive tubing- wherein the beginning and ending of this tubing could be connected to the homeowners remotely placed solar collector. The collector would be nothing more than a piece of black plastic tubing coiled on the rear of the house in rural communities. Believe it or not, there is more than one way to skin a cat, engineers could have little trouble hiding water/ glycol ( remember it is a closed system so any conducting liquid solution would be sealed from the actual hot water in the tank) in many creative fashions. Shingles are excellent heat conductors if they are black so it might even be advantageous to place a conductor behind them if possible. Better still, the peak of the roof line is often used for venting attic air. With not much difficulty the manufactures of these venting systems could offer successive lengths with tubing concealed behind the sections which could be connected to suit the purpose of project. The bigger the house means the bigger the roof, AND the bigger the hot water needs.
   Homeowners could be offered tax credits for using solar hot water systems. It could be calculated down to the single BTU with simple calculating circuitry built into the hot water tanks.
   So why not? If some podunk like me from Ohio can think of this then how come nobody is doing it yet? After all we all use hot water everyday!

   • ANSWER:
     A mandate? This is a good idea but no one has the right in this country to mandate things like this that would cost 20 times as much for a hot water tank.What about the people that make barley enough to make ends meet. Your from Ohio where a lot of people ain't working. They have to take cold showers or not at all? I use cold water for laundry, use the microwave for heating water and a coffee maker. For someone like me that takes one 5 minutes shower a day the electric payback would not be in my life time. They make a timer for a hot water tank that saves. If you use electric and your electric company where to generate through wind and nuclear, or solar (not coal like Ohio does) you would end up with the same end results. There is a enough things mandated in this country, the word mandate to me means loss of freedom. See if you can sell this idea that is affordable to a company.

9. QUESTION:
   How much should solar hot water and radiant heat cost in Maryland, USA?
   I'm getting quotes for a replacement for our hot water heater. So far I've gotten 22K for materials and installation of a solar hot water heater (3-4 collector panels) with heat rejection and single zone open direct radiant heating to one floor (accessible through drop ceiling underneath). Both quotes include a backup hot water heating system; the expensive one would involve installing a new backup high efficiency heater by converting our propane tank to use for heating. This would be either the Polaris or 2 Takagi Jrs, one for the solar hot water and another to power the radiant heat.

   Another quote is for 12K for only the solar hot water and heat rejection using the Velux system.

   Are these really high? I've already contacted 3 companies but it doesn't look like too many people are installing them in Maryland yet. I'm still waiting on a quote from one final company. Thanks!

   • ANSWER:
     Without information of how big the footprint of the house is, and how many people the domestic hot water (DHW) is for, it is hard to say.

     You said you got a quote for 3 -4 collectors, so I'm going to make some assumptions based on that. Four 4'x8' collectors = 128 sq ft of collector. A general rule of thumb for space heating with solar is 1 sq ft of collector for every 5 -10 sq ft of house footprint (depends on heat storage, heat loss in the house, climate, etc). So, if we say 1200 sq ft house, 1200 / 10 = 120; 128 sq ft of collectors could work (again, depending on above variables). Depending on the brand, each flat plate collector could cost about 00, so 00 for the four collectors (evacuated tubes cost more). You then need a controller, storage tank, pumps, heat exchanger, plus all of the copper pipes and fixtures. Then a couple of days for a plumber to install. ,000 installed seems about right without the backup heater. Here's a heating system that costs that just for the equipment http://www.altestore.com/store/Solar-Water-Heaters/Climate-freezes-Closed-Loop-Systems/Combined-Solar-Hot-Water-Space-Heating/Heliodyne-Solar-Hot-Water-Space-Heat-1500-sqft/p6731/.

     Note, gas on-demand water heaters like the Bosch Aquastar make great backup heaters for solar http://www.houseneeds.com/shop/HeatingProducts/WaterHeating/AquaStar1/aquastar1600psmain.asp. I don't know what size you'd need.

10. QUESTION:
    Should you install a solar water heater?
    Should you install a solar water heater? The average home has a 200 liter (50-60 gallon) hot-water tank, which is effectively drained and replenished three times per day. Assume that the entering tap water is 15 degrees C and is heated to 50 degrees C. Given an average energy from sunlight of 1.53 kJ/cm2 per day, how large would the collection area (in m2) of a solar water heater need to be if its efficiency is 28%? Assume that the price of a solar collector is 5/m2. How much would it cost to install this hot water system?

    • ANSWER:
      I don't see how you can go rwong installing it, be it for economic -, environmental reasons or otherwise. In time, the system will undoubtedly pay for itself. There is also the safety factor. Propane can be volatile, something you don't have to worry about with solar. Hot water haeting systems aren't as high tech ( at laest not some) as you might think. You could probaly even install some pretty primitive ones of your own making. You could put a flat rectangular box with a large surface area on you roof, paint it a flat black , and you'll be surpriced at how much it can heat water. And you could just buy the standard hot water heating panels, witha pressure relief valve, and a mechanical heat expansion solar tracking device, or a computer controlled tracking. Pool heating systems , for the most part are pretty primitive, consisting mostly of lots of small rubber tubes bunched together in a mat, all connected to a larger supply , feed and circulation tubes. You could even coil a bunch of metal tubes , and paint them a flat black for maximum absorbtion of solar heat. I'd go solar. All around it's a good idea.

11. QUESTION:
    Is it possible to turn my unused detached garage as a huge solar collector/power plant for my home?
    I live in an older neighborhood, and we have a garage that we never use because it's small and inconvenient. It sits about twenty feet from the back of our house. The garage is masonry block construction, about 18' x 18', and has a hipped roof. It faces due south, and is level with our daylight basement, where we have our hot water heater and gas unit for heating and cooling (newer model). I'm wondering if it makes sense to super-insulate this garage, fill it with water storage tanks or some other material that will hold heat, and add roof windows or solar panels on the south-facing side. I know next to nothing about storing solar energy, or methods of getting the warmed air into the house, but I will definitely do the research and try this if it sounds feasible and worth the effort.
    BTW, I don't have a car anymore. It got vandalized, was a total loss, and one of the best things that's happened to me. I started riding the bus and walking to everywhere I was able, and recently purchased an electric scooter. I don't plan on replacing my car.

    • ANSWER:
      Yes, it has the right location. Make sure no trees cast shadows on it in the afternoon. I have a similar two garage car port that support my four second generation copper solar panels.that heat my 200 gallon solar hot water system. I have a delta-T control system. If you can install the solar hot water tank above your panels by at least a foot you would not need any pump to circulate the water from your solar panel to your tank. I believe it's call a thermal siphon system.

12. QUESTION:
    Price to instal a solar water heater?
    Should you install a solar water heater? The average home has a 200 liter (50-60 gallon) hot-water tank, which is effectively drained and replenished three times per day. Assume that the entering tap water is 13 degrees C and is heated to 55 degrees C. Given an average energy from sunlight of 1.53 kJ/cm2 per day, how large would the collection area (in m2 of a solar water heater need to be if its efficiency is 20%? Assume that the price of a solar collector is 5/m2. How much would it cost to install this hot water system?

    Calculate energy required to heat 1 mL of water. Convert this to tank volume. area=heat required/(solar heat/area)/eff. Installation cost = area x solar collector cost.

    I'm getting 34x10^6 m^2
    12x10^9 dollars to install

    Apparently this is wrong but I can't find my mistakes. Anyone?
    I have 4180 J/Liter giving 837,200 J to heat up 200 Liters of water 1 degree C. I multiplied that by 3 because it's drained and filled 3 times a day giving me 2,511,600J per day. I multiplied that by 42 (55-13) giving me 105x10^6J per day, altering for the change in temperature of the tank. I took that and converted it to kJ = 105x10^3kJ per day. Took 1.53kJ/cm^2 and divided by 1000 to get m^2.

    105x10^3/(.0153kJ/m^2)-----> Divided by .20 for efficiency factor and got 34x10^6 m^2

    34x10^6 m^2 x 375 to get 12x10^9 dollars

    I know this is wrong, but I just can't seem to find the mistake.

    • ANSWER:
      Eyeballing it, about 50 m^2, and 000, which is way out of line with the real world, at least, for Hawaii. Without that 20% efficiency number, the answer would be reasonable for me. I would think 10 m^2 and 00.

      Look up the "specific heat of water", and find out how many joules are needed to heat a gram (= 1 mL) of water by one degree C. That's the same number of kJ needed to heat a liter.

      EDIT:

      "kJ = 105x10^3kJ per day. Took 1.53kJ/cm^2 and divided by 1000 to get m^2."

      105 x 10^3 kJ per day. I agree. But you should take 1.53 kJ/cm^2 and *multiply* by (100 x 100 = 10,000) to get kJ/m^2. So that's 1.53 x 10^4 kJ/m^2.

      Dividing that figure into 105 x 10^3 kJ, you'll get 105/15.3 = about 7 m^2. Then divide by 0.20 to get 35 m^2.

13. QUESTION:
    How do I connect open system solar collectors to space heat my home?
    Hi, I have installed two 300 Liter solar water heating panels with overhead storage tanks.
    I need to know how to connect these panels to the floor heating, radiator diffusers and the hot water tank altogether.
    Schematic diagrams will be more than perfect.
    Thanks.

    • ANSWER:
      solar heaters don't usually get enough sun on winter, so heating the floor will be very hard with a solar heater in winter.

      In order to give you a decent diagram, will need to have a full diagram of your house hot water system.

      Maybe the guys of earthstar can help you.

14. QUESTION:
    anti freeze for a hydronic heat system?
    i am finally finished with my heat system. it's a hot water solar collector, with a heat exchanger from the woodstove. it then travels thru the concreet slab for heat. the problem is that i'm getting mixed messages from people about what type of anti freeze to run in it. the solar pannels will be turned off at night and will get very cold. i was told that i need some special fluid for the system at $ 22.00 per gallon. i need 30 gallons! my origanal plan was to get some recycled anti freeze from a local auto salvage. any thoughts? thanks john

    • ANSWER:
      Check with your local building inspector on this.As a contractor I can not put regular car anti-freeze in a heating system but in our area it is legal for a homeowner to do this.I would strongly recommend that you have a back flow prevention device on the domestic water line that feeds the system[this is code in most places],and if you use car anti-freeze you will want one that has an atmospheric dump instead of just a double check system.Some one has suggested RV anti-freeze,never use RV anti-freeze in a heating system because it is an alcohol base and will evaporate out of the system in a very short time.Now with all that said I would still use the non-toxic anti-freeze for boiler systems rather than used car anti-freeze.Used anti-freeze could be contaminated with oil,heavy metals,and other chemicals and may also be acidic these are things that you do not want to add to a new heating system that you have spent I assume several thousand on.

15. QUESTION:
    Which one... theyre could be more then 1?
    . If you want to use passive solar heating for a home in northern Maine, what structural features would you include?
    _____ Thin glass windows
    _____ Concrete or stone floors
    _____ Large south-facing windows
    _____ Hot water radiators
    _____ Solar collector and pump
    _____ Ceiling fans
    _____ Gas furnace
    _____ Insulation with high R-value

    • ANSWER:
      Any and all of these could be included as you design a passive solar house (though I'm not certain about your "thin glass" term).

      The most important aspect of any home design is energy efficiency. To that end, consider high R-value wall and attic insulation along with great air sealing and good quality windows. As you look to passive solar, siting the home on your lot to afford maximum solar heating will be important, as will thermal mass that the sun can warm during the day that will radiate back to the structure after the sun goes down.

      Active solar solutions such as solar thermal water heating integrated with in-floor hydronic heating might be an option, as would a ground-source heat pump or a masonry stove. Your options are many. Without knowing more about your project parameters, budget, siting, etc, it is hard to come up with specifics.

16. QUESTION:
    Solar power cost effective calculation?
    An average householder uses 160 litres day-1 hot water at a temperature of 55oC, and the specific heat of water is 4.1868 kJ kg-1oC-1 and the inlet temperature of the water to the house is 10°C. Estimate the total energy requirement for hot water supply. If a 2 m2 solar collector is installed to save electricity for hot water supply, the efficiency of the solar panel is 55%. Assuming the mean availability of solar energy throughout the year is 115 Wm-2, the cost of electricity is 5.87p kWh-1, the total cost of the installation is £2000, and it has a life span of 20 years, is the scheme cost effective at a 0% discount rate?

    I got the total energy required to heat the water as 11.47GJ/Annum and that its not cost effective as the solar panles will provide 34.7% of the heating requirement which is equilivent to £1300 over 20 years, thus as it cost £2000 to install, its not worth it.

    Is this correct? I feel i have done it wrong

    • ANSWER:
      My calculations show the panels producing 7.25 GJ/year, and 11.00 GJ as the original electrical requirement. That means the panels would produce about 66% of the heating requirement (oddly, this is the complement of 34%).

      1 kWh = 3.6 MJ, so the annual energies are

      solar 2013 kWh/y
      electric 3056 kWh/y

      The value of the solar heating is therefore 11800p / year. I'm American, but if p are like cents, and pounds like dollars, then that's £118 / year, or £2360 over 20 years, a bare win over the system price.

      It sounds like these calculations are for a place that is right on the cusp of where solar makes sense. In Hawaii, electricity would be 3-4x that price, the system price 2/3 of that (simple panels - freezing not an issue), the insolation 2x that, and the water inlet temperature higher, making the energy requirement 2/3 of that.

17. QUESTION:
    Solar Thermal collector ,?
    I would like to put a tank outside my house and use it for a force hot water heating system, If I can do this what is the best way to do this?

    • ANSWER:
      You will need to insulate it from heat loss somehow.

      You can find a lot of project information here :http://www.builditsolar.com From actual installations to some info on commercial installations. You might find a set up that is actually better suited to what you want to accomplish too. Many are in his projects section.

18. QUESTION:
    Solar Heating Question?
    A hot water heater is operated by using solar power.
    If the solar collector has an area of 5.2 m^2, and the power delivered by sunlight is 1022 W/ m^2, how long will it take to increase the temperature of 1 m^3 of water from 20°C to 51°C? The specific heat of water is 4186 J/kg * °C and the density of water is 1000 kg/m^3.

    • ANSWER:
      OK Well the amount of energy stored by the water is given by

      E = mass * specific heat * temperature change.
      E = 1000 * 4186 * (51 - 29) = 1.3 * 10^8 Joules

      The amount of power collected by the solar collector = 5.2 * 1022 = 5314.4 W

      Recall that 1 W = 1 Joule per second
      So
      5314.4 W = 5314.4 J / s

      So the time = 1.3 * 10^8 / 5314.4 = 24461.8 seconds = 6.79 hours to two decimal places

19. QUESTION:
    Solar collector ?
    Where I live is about 35 C in the shade.So it's pretty hot and I thought I could use the heat to warm up water or something.I want to put a solar collector on the terrace but I'm not shure how to build it.Can you explain to me how ? And please I'm 15 so don't make it too scientific XD

    • ANSWER:
      You can definitely use the sun's energy to heat water. You can even use it to pasteurize water, killing organisms and make it safe to drink.

      Any dark container, black, brown, or dark green will capture the sun's heat. What matters most with solar cooking is not how hot it is outside, it's how much clear sunshine you have. You can even solar cook when there is snow on the ground and the temperature is at freezing -- so long as there is clear sunshine.

      A very simple solar cooker uses a black painted canning jar and lid as the cooking vessel. Then enclose the jar in a nylon oven cooking bag like a Reynolds oven cooking bag. That by itself will heat water.

      If you actually want to cook, or you want to pasteurize water, then place the jar and cooking bag into a solar reflector that you construct out of corrugated cardboard, glue, and aluminum foil.

      There are easy construction plans available free on the internet from Solar Cookers International. This is pretty much how I started solar cooking. This is a very easy construction, and it folds up so you can store it away easily.
      http://solarcooking.wikia.com/wiki/CooKit

      Another easy one is made from a cardboard box, glue, and aluminum foil.
      http://solarcooking.org/plans/newpanel.htm

20. QUESTION:
    Physics: What is the equilibrium temperature of a collector plate directly facing the sun?
    You would like to put a solar hot water system on your roof, but you're not sure it's feasible. A reference book on solar energy shows that the ground-level solar intensity in your city is 650 W/m^2 for at least 5 hours a day throughout most of the year.

    Assuming that a completely black collector plate loses energy only by radiation, and that the air temperature is 20 degrees Celsius, what is the equilibrium temperature of a collector plate directly facing the sun? Note that while a plate has two sides, only the side facing the sun will radiate because the opposite side will be well insulated.

    • ANSWER:
      It doesn't matter how big the plate is, but for the sake of making computations easy, let's assume it is 1 m^2 in area. Then the power of the sun hitting it is 650 watts.

      As the plate is neither heating nor cooling, the power that the plate is radiating must be equal to 650 watts.

      If you don't remember the Stefan-Boltzmann law, you can look it up here http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law . From that, P = s * T^4, where P is power, s is the S-B constant, and T is absolute temperature. Set the left side to 650, and you can solve for temperature. Then convert it to Celsius for a more useful answer.

      I have ignored the temperature of the air on the assumption that when a solar radiation figure is given, it includes all sources, including the air and blank sky. And also, the problem states (unrealistically) that there is no heat loss by conduction or convection.

21. QUESTION:
    how long will it take to in- crease the temperature of 1 m3 of water from 20◦C to 64 ◦C?
    A hot water heater is operated by using solar
    power.
    If the solar collector has an area of
    6.8 m2, and the power delivered by sunlight
    is 1019 W/m2, how long will it take to in-
    crease the temperature of 1 m3 of water from
    20◦C to 64 ◦C? The specific heat of water
    is 4186 J/kg ·
    ◦ C and the density of water is
    1000 kg/m3.
    Answer in units of h.

    The wording of this question confuses me... I'm not sure which numbers I am supposed to use.

    • ANSWER:

22. QUESTION:
    Explain this to me,pllzz:solar power related..?
    im researching buildingd that use solar energy to function,one of the building i found is the vrtical village in dubai,here's an extract of the info i got on it:
    The Vertical Village incorporates the most basic mantras of energy-efficiency in hot climates: reducing solar gain and maximizing solar production. Each hockey-stick-shaped building within the village is self-shading on its north side and on the east-west axis to reduce long-angle sun penetration. A massive bed of solar collectors lies at the south end of the complex and has the ability to automatically position itself toward the sun to maximize solar-energy aggregation.
    The solar roof behaves much like a leaf, with veins that break the solar field up to provide structure but also transport energy, in this case hot water, back to the building where the energy is used to significantly reduce air conditioning consumption and provide hot water.

    i dont understand most of this & i need help!!
    if u can explain anything to me ...plz do!

    • ANSWER:
      Hello Lola,

      i am sorry, i don't have any idea.

23. QUESTION:
    Why only Photo-Voltaic solar panels?
    Photo-Voltaic solar panels are very expensive.

    Most of a home's energy needs are for heating water, heating and air-conditioning. All of these can be met with thermal solar collectors which are much less expensive.

    The thermal solar panels would heat water stored in a hot water tank which then can be used as hot water, to heat the home, or as the heat source to a Lithium Bromide Absorption chiller to air-condition a home.

    With the base line needs met without expensive panels and without inefficient energy conversions, only a small Photo-Voltaic array would be needed for the remaining power needs and since those needs are variable, there would still be power to sell to the grid.

    A solar air-conditioner can be found at http://www.solarpanelsplus.com/solar-air-conditioning/
    It would also seem that solar thermal would be easier for a DIY to manufacture out of inexpensive parts especially if only used as preheat in the absorption chiller. Such panels have been made from beer cans before though copper pipes would be a better choice. Inexpensive rubber panels are typically seen in Hawaii.

    Typical payback periods for Solar Thermal is two years. Typical installation cost is ,000 after tax credits.

    The absorption chiller is actually a proven gas fired chiller modified to use hot glycol as the heat input. It's technology with lower operating costs when used with natural gas than electric mechanical compressor chillers but a higher capital cost. It does require 90 C input hence the active evacuated tube solar but a hybrid of solar preheat and gas fired would work too.

    • ANSWER:
      Just read some of the other posts and I am surprised at the answers. Solar thermal systems typically have a payback of less than seven years on residential system without the tax break. A complete system can be installed for about 5k or less. Compare that to 20k or more for PV with a fifteen to twenty year pay off.

      Each home and area is different so a site evaluation must be done for exact figures and pay offs. I am going off my own experience in my above statements

      Flat panel collectors work well in most areas for DHW. Evacuated tubes often run too hot which works well for some applications or high usage.

      Heating water is the single greatest energy usage other than space heating and cooling. It often surpasses the two above systems based on its widespread usage(every houshold in USA has one) and its the amount it is used(24/7@365)

      The amount of energy spent to heat water is by order of magnitude the greatest number out there.

      Having a solar thermal system providing hot water for a average American household is equivalent to taking 40,000 miles off the freeway in a car every year. The BTU's required to heat the water is huge.

      So why is this more developed cheaper and more efficient technology behind PV in awareness?

      Natural Gas the number one choice for heating water is cheap. It's by product is invisible and misunderstood.

      What I find fascinating is if you look at the increase in Natural Gas vs Electricity you will be surprised by how much it has jumped in the last seven years. It is not talked about nearly as much as electricity

      It does not get the same level of press that PV does.

      So in short the answer is cheap Natural Gas prices and public perception of this product have kept it off the list of many that are turning toward the green trend. It is less sexy than watching your meter spin backwards.

      It is the best improvement at the best cost except for conservation which is and was the most cost effective energy saving that can be employed

24. QUESTION:
    I hope you can answer this if you're an engineer!!!?
    You have been asked to design a solar water heating system for a family of four. The family uses 100 gallons per day of hot water at 50 degrees Celcius. The cold water enters the house at 5 degrees Celcius. The solar collector heats the cold water to 75 degrees Celcius and stores it in an insulated storage tank until the family needs it. The sun shines for an average of 7 hours per day and provides 235 Watts per meter squared. Determine the size of the storage tank and the size of the collector.

    • ANSWER:
      Sattra has it dead on.

      The hot water will be mixed with cold to give you 50 degrees. Simply set up:

      75(X) + 5(100-X) = 50(100)
      X = 64.28 gallons
      Where X is the amount of hot water added to the mix

      Now calculate your heat duty required per day
      deltaH = (1cal/g*C)(243375.5 g)(70 C)
      delta H = 17036285 calories/day

      Do a conversion of the power to get your energy output from the solar panels

      (235W/m^2)(.01433kCal/min*W)(60min/hr)(1000g/kg)
      output = 202053 cal/m^2*hr

      Multiply by your daily ration of sunshine
      (202053 cal/m^2*hr)*(7hr/day) = 1414371 cal/m^2*day

      And divide into your required heat duty
      (17036285 cal/day)/1414371 (cal/m^2*day)

      Total size of collector = 12.05m^2

25. QUESTION:
    physica word problem help please!!!?
    A hot-water heater is operated by solar power. If the solar collector has an area of 4.3 m^2 and the power delivered by sunlight is 550 W/m^2, how long will it take to increase the temperature of 1.0 m^3 of water from 21°C to 63°C?

    • ANSWER:
      ♦ power received by collector p=b*A, where A=4.3m^2, b=550W/m^2 is specific density of solar power;
      ♥ work done by Sun w=p*t, where t is time of shining;
      ♠ this work is gone to heat the water w=c*m*T, where c=4.19 kJ/(kg·1°C) is specific heat of water, m=1000 kg is mass of 1m^3 of water, T=63-21=42° is temperature difference gained by water;
      ♣ thus b*A*t = c*m*T, hence t= c*m*T/(b*A) =
      = 4190*1000*42/(550*4.3) = 74410s =20hour 40 min;
      Summer in Alaska?

26. QUESTION:
    HELP???PHSYICS-dont understand?
    A hot-water heater is operated by solar power. If the solar collector has an area of 5.7 m2 and the power delivered by sunlight is 550 W/m2, how long will it take to increase the temperature of 1.0 m3 of water from 25°C to 60°C?

    • ANSWER:
      easy.... Cp water = 4186 J/Kg.K

      Power = 550 * time = mass * Cp * dT
      mass= 1000 kg (1m^3 - more or less)
      dT = 35

      So, time = 1000 * 4186 * 35 / 550 = 266 381 seconds = 74 h

      Considering that all the energy is converted to heat... that's partially FALSE ! But that's the only calculus i can do using your data

27. QUESTION:
    Physics HELp?
    A hot-water heater is operated by solar power. If the solar collector has an area of 5.9 m2 and the power delivered by sunlight is 550 W/m2, how long will it take to increase the temperature of 1.0 m3 of water from 25°C to 61°C?

    • ANSWER:
      1W = 1J/s
      So heat delivered is rate*area
      5.9m^2 * 550 j/s*m^2 = 3245J/s
      c = Specific heat of water = 4.186 joule/(gram*°C)
      density of water is 1g/mL
      1000mL = .001 cubic meters
      m = 1,000,000g
      ΔT = 61-25 = 36
      ΔQ = heat required to reach desired condition
      ΔQ = mcΔT
      = (1*10^6g)[4.186 joule/(gram*°C)](36°C)
      = 150,696,000 joules
      ΔQ/heat delivered = time
      150,696,000 joules/(3245J/s) = 46439 sec
      OR 12.9 hours

      Do you really think that it will take 2 minutes to raise that much water 36 degrees?

28. QUESTION:
    Heat Problem?
    A hot water heater is operated by solar power. If the solar collector has an area of 6.0m^2, and the power delivered by sunlight is 550W/m^2, how long will it take to increase the temperature of 1.0m^3 of water from 20'C to 60'C?
    the answer is 50600s=14hr..
    please explain how to get that answer.
    thanks

    • ANSWER:
      conservation of energy i.e.
      energy delivered by sun=energy necessary to heat water
      supposing that no loss of energy takes place
      PAt=mc(t(f)-t(i))
      or
      t=mc(t(f)-t(i))/PA=1x10^3x4.186x10^3(60-29)/550x6 seconds
      the specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C
      put your computer to work!

29. QUESTION:
    who wants to help me with physics thermo problems?
    yeah so basically i have no idea how to do these problems because my teacher hasn't taught our class anything. if you like thermo problems you should help me! (and if you respond with 'do your own homework' or w.e., idgaf i'm lazy and confused =_=)

    The gas in a constant-volume gas thermometer has a pressure of 89.0 kPa at 109°C.

    (a) What is the pressure of the gas at 50.0°C?

    (b) At what temperature does the gas have a pressure of 115 kPa?

    A jar of tea is placed in sunlight until it reaches an equilibrium temperature of 39°C. In an attempt to cool the liquid, which has a mass of 195 g, 112 g of ice at 0.0°C is added. At the time at which the temperature of the tea is 15°C, determine the mass of the remaining ice in the jar. Assume the specific heat capacity of the tea to be that of pure liquid water.

    A 330 g aluminum cup holds and is in thermal equilibrium with 810 g of water at 83°C. The combination of cup and water is cooled uniformly so that the temperature decreases by 1.5°C per minute. At what rate is energy being removed by heat?

    A student drops two metallic objects into a 120 g steel container holding 150 g of water at 45°C. One object is a 253 g cube of copper that is initially at 85°C, and the other is a chunk of aluminum that is initially at 10°C. To the surprise of the student, the water reaches a final temperature of 45°C, its initial temperature. What is the mass of the aluminum chunk?

    A hot-water heater is operated by solar power. If the solar collector has an area of 6.0 m2 and the power delivered by sunlight is 550 W/m2, how long will it take to increase the temperature of 1 m3 of water from 23°C to 61°C?

    A plastic-foam container used as a picnic cooler contains a block of ice at 0.0°C. If 255 g of ice melts in 0.8 h, how much energy passes per second through the wall of the container?

    A 81 kg cross-country skier moves across snow. The coefficient of kinetic friction between the skis and the snow is 0.20. Assume that all the snow beneath the skis is at 0°C. If all of the energy is absorbed by the snow, how far would the skier have to travel in order to melt 1.3 kg of snow?

    When a driver brakes an automobile, friction between the brake disks and the brake pads converts part of the car's translational kinetic energy to internal energy. If a 1640 kg automobile traveling at 39 m/s comes to a halt after its brakes are applied, how much can the temperature rise in each of the four 3.5 kg steel brake disks? Assume the disks are made of iron (cp = 448 J/kg·°C) and that all of the kinetic energy is distributed in equal parts to the internal energy of the brakes.

    A 33.7 g ring that appears to be silver is heated to a temperature of 84°C, and then placed in a calorimeter containing 5.00 multiplied by 10-2 kg of water at 24.0°C. The calorimeter is not perfectly insulated, however, so that 0.14 kJ of energy is transferred by heat to the surroundings by the time a temperature of 25.0°C is reached. From the information provided, can you determine the specific heat capacity of the ring? Is the ring truly made of silver? (Refer to Table 10-4.)

    thanksss!

    • ANSWER:
      use the formula PV=nRT

30. QUESTION:
    How calculate PSI/Flow in a Thermosyphon?
    How could I calculate the PSI/Flow rate in a solar powered themo siphon? I know I can build a solar heat collector and a tank to store the water, but what kind of pressure/flow will be in the system? I am also assuming the greater the differntial in temperature of the water in the tank and the heat in the collector the pressure/flow I will have. Does that means when the water finally gets hot and the collector and water temp are somewhat close to matched I will have no pressure?

    THANKS!

    • ANSWER:
      The pressure difference in a thermal circulation hot water system is given by (this can be used for any type of hot water boiler fed system without a circulation pump) :

      deltaP = h(Dr - Dd) = h(1/Vr - 1/Vd) Where:

      deltaP = pressure difference for water circulation in lbs. per sq. ft., and is the pressure available to overcome friction
      h = difference in elevation between the heat source and the radiator in feet.
      Dr = density of the return water in lbs. per cu. ft.
      Dd = density of the delivery water in lbs. per cu. ft.
      Vr = specific volume of the return water in cu. ft. per lb.
      Vd = specific volume of the delivered water in cu. ft. per lb.
      use a table of thermodynamic properties of water and steam to determine Vr & Vd.

      To express the deltaP pressure drop in milliinches of water instead of lbs. per sq. ft. use

      deltaP = 193h(1/Vr - I/Vd)

      Note that you will want a shutoff valve in front of your boiler or heat source, a shutoff valve in front your radiator, an air bleed valve at the high point of the radiator, and a vented expansion tank connected to the boiler water feed line to the radiator, and installed at an elevation higher than than the radiator.

      When the water temps are the same you will have no flow.

31. QUESTION:
    solar hotwater system homebuild?
    I have gravity fed cold water from tank and need info. possibly a diagram on the homebuild of a solar hotwater system for rooftop. copper pipe or other in tray with hot tank collector. Where does cold go in to lines and where hot out to collector tank.?

    • ANSWER:
      There are many different kinds of solar hot water systems. Some are active systems that use pumps, but there are also two types of passive systems that do not. The distinction is whether it is a "batch" ( or "breadbox") heater which is essentially a tank in an insulated box that gets warm and stays warm or there is also a system where there is a tank that is placed above a collector. In this system convection circulates the water through the collector. It is known as a thermosyphoning system. As the warm water is pushed to the top it moves to the tank. See references below, but exact plans have to be modified for your climate and how much hot water you need.

      These passive systems do not require water that is under pressure (pumped) but the performance of any gravity fed system will improve with larger pipe sizes. PVC should not be used for potable water but CPVC, ABS, or polypropylene can be used as well as copper, cast iron, steel or galvanized.

32. QUESTION:
    Absorption chiller for home?
    In considering a solar concentrator/collector system for heating in the winter, I was wondering if the hot water could be used to cool the house in the summer using an absorption chiller.

    I have seen a few units but all were huge, 100 tons and up for commercial or industrial applications. Can you point me to a source for a unit perhaps in the 2 ton range for cooling a house?

    • ANSWER:
      This seems to be the only company that makes residential size Absorption cooling systems from 2 to 5 ton.

      Good luck

33. QUESTION:
    I need to know if these are true or false and if they are false what goes in the place of the all caps words.?
    1.The transfer of thermal energy by conduction and convection DOES NOT require matter
    2.The transfer of thermal energy by radiation DOES NOT require matter
    3.A material that allows heat to pass through it easily is and INSULATOR
    4.Insulation rated R-35 allows MORE heat to pass through it than insulation rated R-1
    5Solar collectors are used in PASSIVE solar heating systems
    6A solar heating system that does not use fans or electrical devices is AN ACTIVE solar heating system
    7A steam engine is an example of an INTERNAL combustion engine
    8.The fuel of an external combustion engine is burned OUTSIDE the engine
    9.A STEAM-HEATING system uses radiators to transfer thermal energy
    10.Refrigerators and air conditioners are HEAT PUMPS
    11Steam-heating systems require MORE water than hot-water systems
    12cause dark colors REFLECT more radiant energy than light colors, solar collectors are usually painted black
    13Many external combustion engines are TURBINES to produce mechanical energy

    • ANSWER:
      1. False, Does
      2. True
      3. False, Conductor
      4. False, less
      5. True
      6. False Inactive
      7. False external
      8. True
      9. False, Water-heating
      10.True
      11. True
      12. False, Absorb
      13. True

34. QUESTION:
    How Close Would Water Need To Be To The Sun In Space For It To Boil?
    How close would water need to be to the Sun in space for it to boil??

    In order to generate electricity we heat up water and use the steam to turn turbines so I was thinking that if you built a powerplant in space and had it a certain distance from the sun the water would boil from the heat and the steam could be used to turn turbines, turbines that would move much more quickly because of the lack of earth gravity.

    So the Sun boils the water, the water steam turns turbines and then the steam is passed down pipework AWAY from the sun where it cools back down into water. That water is then pumped back towards the sun where it once again boils.

    The internal systems such as any pumps for pumping the water and steam could be powered by external solar panels.

    The electricity generated from the turbines is converted into a focused beam of Microwaves which is fired towards Earth and collected by an orbital collector and beamed down to Earth.

    The size of the space based powerplant IMO is the bigger the better. The boiling water turning turbines method will create more energy than simply having solar panels. You could have just one large powerplant or several small ones.

    I would think it would need to be pretty large in order to get a powerful enough microwave beam to reach Earth. To ensure a full beam reaches Earth there could be several 'collector relays' along the way which convert the mircowaves to power and create a new focused microwave beam. power will be lost en-route but power should still reach earth.

    Another use for such a powerplant would be a space based colony (something like jupiter Station on Star Trek capable of holding a large number of people).
    Perhaps a space based colony orbiting Venus, it would be closer to the powerplant and would gain more power from it.
    Would an orbital space colony be capable of orbiting Mercury?? I'm not sure if it would be too hot for humans that close to the Sun?

    Perhaps one day there would be a massive array of these powerplants all connected in some kind of net around the Sun channelling all the power into a single microwave beam.

    Maybe one day we will have batteries that can store enormous amounts of power. The powerplants all work together to charge a large battery which is transferred to Earth orbital periodically where it beams the power down. As one battery leaves for Earth another fresh battery arrives for charging.
    THE WATER WONT BE IN SPACE! IT WILL BE INSIDE A NON-VACUUM MACHINE!

    • ANSWER:
      Otter is correct. Water would boil in the vacuum of space, even at a low temperatue. The distance from the sun is not the issue. It would only need to be warm enough to not turn to ice.
      If you place room temperature water in a cyllinder and pump out the air, the water will boil at that temperature. (When a near vacuum is reached.) This is often done as a demonstration in science classes.
      *****
      OK Now I see you have added the comment that the water is not in space, but is in a closed non-vacuum container.
      In general, your idea might work. It has at least one very large problem, though. It would be enormously costly to move all that water and material into space. A competitor could easily supply the electricity much cheaper with a ground based system.

35. QUESTION:
    summary very short please?
    I'm italian and I need a little summary of the follow subject: " THE ACTIVE METHOD uses specially designed heat collectors where, commonly, the storage medium is water, then the heat can be transported by low-power electric pumps (sometimes by gravitation) to a main storage tank to supply the hot water, or circulated to radiators for space heating.
    PHOTO VOLTAICS (PVs) this is perharps the most exciting area because it is capable of supplying large amounts of energy both on a local and more central scale.It is also interesting because the devices (the cells modules or arrays) are constantly being improved by research and development, and production costs are being reduced. Most of us are familiar with the solar panels used in the space programme, well the reality on the ground is similar. Normally a large array of cells is interconnected and positioned sensibly to expose the surface area to the sun as much as possible" .
    I need it short and with easy words, thank you everyone for your time!!

    • ANSWER:
      (I'm assuming both of these are related to alternative energy production)

      Summary:
      The power of sunlight can be captured in a number of ways. One way, called the Active Method, collects the energy of the sun in water (in hoses arranged on the roof, for example). The water in the hoses is heated by the sun and we can use gravity to transfer this heated water to a main storage tank to supply hot water for washing, or heat the house through radiators.
      A second way to use solar power is through photo-voltaic cells (PVs). Sunlight is collected through a large number of solar panels which are connected to each other and aimed to get the best exposure to the sun. The energy from these panels is stored in batteries, and can provide for some or all of the electricity needs of a home.

36. QUESTION:
    wondering about desalinization of seawater....?
    at what temperature does ocean water turn to water vapor and clouds?.... I'm guessing it's quite a bit below boiling, as seems to be necessary in a 'still' to get the steam to become 'fresh' water..... so.... could we kill a couple of these birds by something like this?.... running salt water thru black pipes to warm up in the sunlight, maybe in the same place as the solar collectors for elec power?, then out to holding ponds with plastic over them for the condensate to collect and run off....moved by pumps powered by windmill turbines? seems like this would work good in the desert... hot days, cool nights for the condenseate to work?.... of course, we'd have to pump it from sea to desert, right?... same windmills?....

    I'm prob pretty far out, but there's gotta be a way for us to get that water made useful to those who need it!!... got any other ideas out there?....
    thanks, you two, for indulging me and my outlandish ideers.... I'm glad someone else is tossing ideas around, tho.... this seems like one of the most important problems just now.. I hope it's soon solved...

    • ANSWER:
      That is one idea. I´ve been thinking about a glass structure. Maybe a hybrid. A half pipe, black in the bottom to absorb sunlight and covered with glass to let light in and trap the heat. If its airtight you can use a compressor to suck the humidity out while lowering the pressure in the structure which makes it easier for more water to evaporate. The vapor sucked out is compressed into a tank until it becomes liquid again. This also raises the temperature quite alot. You use fresh, cold seawater to cool it down in a heat exchanger. Now the freshly produced freshwater should be cool enough to be pipe-lined to where it is needed. The seawater that got heated in the exchanger is pumped into the beginning of the pipe. This way to will have utilized the heat contained in the evaporated water. Watervapor <=> water + heat.
      The compressors and the various pumps will consume electricity. Those can be powered by photovoltaics. Conserving as much energy as possible is key to making the thing realistic. Oh, and there are alot of places where ocean meet desert. Northafrica, Arabian peninsula, Australia, Golfo de California (Mexico), Namibia, Chile. Pumping seawater to the desalinization plant may not be the best idea. Where would you put the brine? The saltwater leftover? Some might be turned into salt but it would be better to pump it back into the ocean I think.

37. QUESTION:
    Obama "Green" Energy plan - your thoughts?
    Here's a link to Obama's energy plan: http://www.barackobama.com/pdf/factsheet_energy_speech_080308.pdf

    Here's what I think:

    Whilst I am sure Obama wants CLEAN, SAFE energy,
    I am far from certain the people are going to get it.

    There is no such thing as "safe nuclear power..."

    Obama should offer incentives to industry so they develop handy, efficient alternative energy production and storage kits, using a wise combination of solar (especially for hot countries) (round cells / collectors embedded in roofs, walls... not panels) (note: solar work on day-light), wind (i.e. mini-turbines, with paddles, not blades), and water power (EG. water wheels fitted in mains pipes) - there is plenty of profit to be made selling these and the savings made by not investing in a new grid will more than cover incentive payments.

    This way, domestic and business users will be self-sufficient and the USA will have Energy Security i.e. nobody will suffer power cuts
    EG. during ice storms, flooding...

    Investment in solar technology really needs to be stepped up hugely.
    If we find the perfect way to a) create light b) use photons to generate electricity c) store that power - all our transport needs will be solved.

    That energy source could also take us to Mars and beyond.
    So instead of politicians concentrating on how to keep fossil-fuel suppliers in the money, and protecting that, whilst ignoring market needs, Obama should prepare the USA
    (and the rest of the world)
    for the new generation of transport which does not require the carrying of flammable / explosive fuel, which is very heavy...

    (More FREE info. my website: http://www.the-alternative.org.uk Chapter 6:Energy / Alternative)

    http://www.physorg.com/news111670954.html
    E.F.Hutton: I strongly disagree with your answer. We do get electricity from light - that is how solar works.
    And I repeat, nuclear power is NOT safe. "If the public knew the facts and if they were allowed to chose between nuclear power stations and candles, they would chose candles."

    • ANSWER:
      I really disagree with the above poster. It's always productive to search and try new methods to solving our problems. It's how science works. We may invest a great deal of time and effort into a single promising approach only to have it fail in the end. But then we'd know more and can better prepare a new one.

      My only complaint is that Obama seems determined for our renewable energy sources to be developed here. There are actually two very promising energy plans being done in the UK and Canada atm. One involves tides and the other man made tornadoes. It made not be made in America but good ideas are good ideas regardless of where they come from.

      Fuels for cars do need to be reliable and rather set as they require massive amounts of infrastructure. But what the above poster fails at realizing is that what is needed is a better way to produce electricity. If we can do that in a cleaner fashion it's much easier to make use of cars that can use existing and proven technology.