Solar Panel Cooling Possible.

SystemSystem Posts: 2,511 admin
Hello all. Very new to the topic of RE and off-grid power.

First off, I am looking to build on off-grid house. No options of having grid system.

My house demands are fairly large as It will need to have air conditioners.

Right now I am looking at mitsubshi City Multi system as it seems to be a lower powered system. A bit expensive, but will definately save on the system I need. ANy other ideas?

Anyway the house will be located in Mexico. So it is usually fairly hot.
http://www.cancuntravel.com/cancun-weather.asp

Also can not find the wind charts but it is ocean front property, with averages between 8-13mph for different months.


My main concern will be about heat losses. I mean it can be very sunny here. Looking at about 50 days a year with precipitation , and most of those day have at least a few hours of sun.

This climate will be excellent for a hot water solar system, but I was wondering if I could mount a large PV system, then the Hot water system underneath the panels. Underneath, used a heatsink to the PV system. Obviously the hot water system will not run nearly as hot in the shade, but I am thinking of just regulating the PV temps to maybe something around 100F-110F. AS I would imagine the efficiency of the solar hot water would be very poor, I would imagine the large size of the system would offset inefficiencies, and also help the solar power be more efficient. As you can see some sort of heat sink to dissipate PV temps would help year round.

If something could be done, would think of running a two loop system for the hot water system. One to cool the PV panels. This system inlet water temps of something around 75-80 degree temps. The outlet temps would hopefully be something around 100 degrees. Not too hot as I want it cooling the PV system not just heating water then having both at high temps. Then every X minutes have the hot water flushed to a strictly Hot water solar array. Something to just take the temps higher.

I am just fairly concerned about temperature.

As a note I am thinking of something in the line of a 5-6kw of solar panels, so I believe this would be large enough to at least investigate cooling the panels.
Definitely have a 10kw generator. And hopefully see what actually usages will be as. I have projected between 10kw-60kw per day depending on time of a/c usage, pool filters pumps, possible jacuzzi usage, light usage etc. I really can not narrow it down better as it will be a rental property. Obviously if I lived in such a place I could conserve energy, but really can not do too much about a paying guest. I expect around 25kw -30kw daily usage.
Everything will low energy usage so it really depends if they live in the house air blasting for a vacation or visit things and are of less demand.

Anyway not sure if it is a poor idea, just like things to run more efficiently. Just think if a small solar hot water can do X. What will the temps be of a Larger PV array.

Thanks for any help/ guidance hope I did not ramble to much.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: Solar Panel Cooling Possible.

    To predict how much power you will get from your solar panels... Look Here (hmm Mexico is not listed--if close to US or Caribbean, use one of those site). For the "DC to AC Derate Factor:", use ~0.52 for an off-grid system.

    Solar PV is not cheap... A really rough guess would be around $1.00 per kWhr (in the states, we are usually around $0.10 to $0.20 per kWhr).

    Also, Off - Grid Solar PV works best if the power is used pretty much year round. If this is a "summer place", then 4 mouths of the year you are using the power generated and the other 8 months of the year the power is lost (so now, $1 becomes $3 per kWhr).

    Placing hot water collectors under the solar panels... You might be able to do this for heating a pool (low temperature solar). However, it will not work well for domestic hot water use and will not help keep your solar PV cool (for better efficiency).

    As of this time, a few have played with trying to cool solar panels (as simple as spraying cool water on them)--but it does not appear to be worth the effort. Your panels will do pretty well in the hot weather (I can see a 5-10% drop in in power between 60F and 95F weather at my home). Not worth the costs or issues of trying any active cooling for a standard solar PV array.

    Best bet is to have the solar panels 6" or more above a roof/surface. And have your solar hot water panels directly exposed to the sun.

    5-6 kWatts of solar panels is a good sized array. Assuming you can get solar panels at $5 per Watt delivered to your door in Cancun--that is $30,000. And, just a guess, but a battery bank for that sized system will cost you another $15,000 to $30,000 too...

    Add another 50% for cost of controllers, inverters, wiring, shed, labor--and you are talking about some pretty big expenses (these are all just wild guesses based on typical US prices--I don't have any idea about costs in Mexico for these items).

    Anything you can do to help reduce power use (insulation, building back into a hill, natural ventilation, etc.) would be a big help.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Solar Panel Cooling Possible.

    Hello BB. First thanks for responding, maybe solar guppy can chime in as his weather maybe similar to mine.
    I would say weather here is very similar to weather in Florida, but seems to be more sun here. I know certain parts of Florida can be very rainy.

    Also as for location it is about 60 feet from the ocean. The almost constant breeze will help. The house(top of pilliars will be located about 10 feet above sea level as the lot is about 5 feet above sea level. There is a natural reef of shore so really no waves very calm water but fairly breezy. Not sure how much breeze/wind helps temps.

    It is very flat. And only swamp type environment behind me.

    Yeah I was looking at prices. Alot actually, and was very happy to come across these forums. I saw solar guppy recommends the Evergreen panels as fairly reliable.

    I was thinking of the Generics Evergreen panels. http://sunelec.com/index.html the sun-190, I believe I understood, it is exactly like the evergreen panels but just have to make sure before I buy.

    As I have not built house yet I plan on waiting for a deal, I do not know how much the prices fluctuate on that site, but I read last week had sun 180's for 2.50/watt. Also not sure on what types of deals this guy gives on bulk, as I am actually looking at building 2 houses next to one another, and so I would be looking in the 10-12kw range to cover both houses. That with other possible equipment from him. Hopefully I can work something out.
    Obviously very excited to be dealing with RE as it is exciting to design for, but there is also a dollars and sense to deal with.


    Obviously thpse prices are undelivered, but That is where I am not in too bad of shape. Closes town to me has a port that takes ships from Ft. Lauderdale direct. Large Cargo ships. Not sure how much actually shipping, but probably not too bad. That shop sunelec is located in Miami.

    If I had a choice I would definitely choose on grid. But there is not electricity at the property. SO off grid is my only choice. It will have a 10kw generator to help out.

    As for other things there are Outback distributors and installers here, just researching everything first before I talk to anyone trying to sell me anything. I am thinking of using outback products.

    AS for batteries I am thinking of forklift batteries as they can be cycled a little more and maybe can buy refurbs at a fair discount They will be a bit of money to get here. I know forklift batteries need a bit more maintenance but it does not seem to be to bad. But they seem to have fairly good life. If I get close to 8 years I would be happy.

    As for the house, will be a vacation house/ investment as it will be rented out as well, all throughout the year. As it will being rented I can not control their electrical uses. I am also going to have a 10kw propane generator so when the batteries hit their lows I will charge batteries up. Also a reason I like forklift batteries as they can be charged fairly quickly.

    All electrical power consumption in the house(excluding a/c) will be about 10kw a day (max). That is 3 pumps(well,pool, house) tv, computers, the whole works. Obviously all heating is done by solar or propane. It is not too bad. Would average at most around 300kwh/month with occupants of a 5 bedrooms house. Obviously the most expensive part is the darn a/c. That is where I am having the issues as I am not a magician.

    Only running a/c in rooms cuts it down a bit, but I still need a 5 ton Mitsubishi city multi unit. Average power consumption is about .35-.5kw per ton. That is if it is running. At the high end of that is 2.5kw/hour but depending on how many rooms are running as the unit can scale back and act as a 1 ton unit if that is all that is needed. So the a/c will probably average 1.5kw/h when a party of 6 is in the house. But also depends on if they are in the house all day. There are different types of vacationers. Most will only run a/c when they are in the house at nights. Still demanding a fair amount of energy but for a group of 6 that would be about 1.5kwh for maybe 10 -12 hours a night.
    Probably looking at 20 kwh of a/c a day with most guest. Obviously could sky rocket, but I expect that to be only a select few weeks of the year. Also the city multi mitsubishi as I understand it very good at dehumidifying as that will allow the ac to run a little hotter but still comfortable. I really have to see what the total house usage will average then maybe add more panels as neccessary. I do not mind running a generator a few hours here and there when need.

    Obviously everything thermically possible within reason is being done. All sun facing windows will have thatched roofs overhanging arbors(spelling) over them This will be esthetically pleasing as well as block direct light entering the house


    Solar guppy let me know how temps are effecting you.
    Thanks
  • newenergynewenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Solar Panel Cooling Possible.

    I haven't used these and have nothing to do with the company. I just saw them at a trade show.

    http://www.sundrumsolar.com/
  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: Solar Panel Cooling Possible.

    Interesting... Says 25lb weight--is that per panel? Might make them a bit more difficult to install.

    Wonder what the panel mfg. would say regarding warranty...

    For my home, where my solar panels take up pretty much the entire prime roof space--being able to add water heating without having to tack on more panels to the side of my home looks interesting. However, looks like they are sized to the brand/model of panel (Sanyo and Evergreen only at this time?).

    Bit concerned about tying a relatively maintenance free product like solar panels with plumbing.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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