Learning about Solar Power
June 29, 2011 2:24 PM   Subscribe

I want to look into planning a solar panel solution for my home, as electricity has hit 50c/kwh and doesn't look like it's ever going down. Where are the best resources online to learn about the various options and techniques?

Electricity has just hit 50 cents per kilowatt hour on our island, and so my mind turns towards what other options are possible. I live in the caribbean, so the sun is hot and steady for the vast majority of the year.

I really want to get a good round knowledge about what's out there, I'm pretty nerdy about tech, so I'm more the happy to delve into the technical aspect, but ideally I'd like a nice learning curve. I imagine if it's a feasible to use technology in the USA, it's a slam-dunk here where the electricity costs are far higher (though there are no government grants here).

Currently, and likely for the foreseeable future, we are unable to 'feed the grid' because the only power company doesn't (won't?) support it.

I imagine you can likely chart my power usage with the amount of available sunlight, as the primary power drain is the air conditioning, so I'm interested if there are solutions available to offset the grid. So, say I have 1kw of panels on the roof, and the A/C sucks 3kw. A magical box will use all the available solar energy, then fill in the blanks with the grid, that way can have a simple system without battery banks and the maintenance associated with them. Of course, if batteries are the better solution, great!

I'm looking for any blogs about people who have walked through the process, or infomational sites that give you a great run through would be more then welcome.
Also, I'd love to hear your opinions on if it's really worth it, or suggestions on the multitude of things I haven't thought of.
posted by Static Vagabond to Home & Garden (10 answers total) 18 users marked this as a favorite
For getting an estimate of how much energy your future PV system could generate, and how much it might save you, try PVWatts. We had our 4.3Kw system installed professionally last year, but in researching, I found Build-It-Solar to have a good collection of information.
posted by jaimev at 2:40 PM on June 29, 2011

As far as I know you'll need the battery banks to help manage the load and draw as the output from solar panels doesn't usually have the amperage to directly run heavy loads like an AC unit.

If AC is your primary draw, you should strongly consider passive cooling solutions you can add to your house, even if it's in lieu of adding solar as well. Planting trees for shade is an easy start, but you can also build shade walls that stand off from your house and then use a thermal mass - like water in barrels, or sealed in recycled glass bottles set like bricks in concrete - to help keep things cooler during the day. Passive cooling is much cheaper than solar panels and the battery bank and inverters required to feed an alternating current AC motor and pump.

Passive cooling has a lot of other benefits as well. Increased building or wall strength if it's engineered correctly. It's a low-impact solution not requiring lead-acid battery banks, or batteries that use other heavy metals like lithium. It's low or zero maintenance



Other traditional solutions would be building with cob or adobe for passive cooling and thermal insulation.
posted by loquacious at 2:53 PM on June 29, 2011

Anyone living in New York City might find nycsolarmap.com helpful. It calculates the value of solar panels on any roof in the city, based on the topography of the city skyline... like if there's a much taller building next door that keeps your roof in the shade, the calculator will take that into effect. Pretty cool stuff.
posted by mark7570 at 3:06 PM on June 29, 2011

I am an electrician in Florida, and have helped install a few solar systems.

Most new home solar systems are connected to the power grid. Solar acts as a supplement to your existing power source. These systems can be set up to back feed the grid (selling your excess electricity), or not back feed (you can not sell your electricity).

Very few systems have batteries these days. Batteries require serious daily maintenance. You do not want vthat. You also do not want a system that requires a converter. AC/DC converters can be a hassle too. (Solar panels produce DC power, your house uses AC power). They make solar panels now that have micro-converters built into the panel itself.

A first important question is does your property have a spot for solar panels. It is not correct that you can use any old roof. You need a south facing roof, or clear land with no shadows from trees or buildings.

I don't know where in the Caribbean you are, but there are gov't financial incentives in the US and European territories in Caribbean.

I would suggest research getting a decent DIY system, then hiring a licensed electrician to install it.
posted by Flood at 5:10 PM on June 29, 2011 [1 favorite]

Honestly doing this yourself would be a major undertaking. You should really (really!) seek out a solar installer in your area to help you. Many of the issues are local, especially with respect to electrical codes (if any) that apply to the installation. At the end of the day you want a safe and productive system and its really easy to screw up one or both of those without a lot of experience. I speak as an electrical engineer who has a professionally installed 4kW home system in California and works in the solar industry.

That all said, systems can be either on-grid (sometimes called grid-tie) or off grid. You really want a grid-tie solution. That way you get your power first from your solar panels once that is maxed out it comes from the grid. These systems are fairly basic. The only 'magic box', is called an inverter and it converts the DC power from the panels to AC. That AC power hooks into you home supply (on the home side of your utility meter). You probably have to have a new electric meter installed from your utility that is compatible even if they won't credit you for the extra power you produce. This really depends on the local issues and why you need to find a local installer/electrician to help.

Off grid systems are quite a bit more complicated, they require battery banks to store what you generate for times when you need more output than your panels can provide (like nighttime). You really don't want to deal with this if you have any choice.

In any residential installation shade is a major consideration. Even partial shading of one panel can degrade the whole system very significantly.
posted by Long Way To Go at 5:17 PM on June 29, 2011

I just had a 'solar installer' come by and give me a quote. Last year the certified installers were able to get language added to the rebates available which dis-allow diy pre-engineered solutions. Rebates are essentially 50%. Magically, the quoted prices were double the diy route.

LWTG: Isn't the partial shading issue resolved with micro-inverters, which seem to be standard these days?

OP: I'd take the passive route first, optimize it, and by the time you are ready for solar pv, the prices will have dropped, and the technology will have improved.
posted by mmdei at 6:52 PM on June 29, 2011

You might find it useful to look through the Home section of the Los Angeles Times on line. They have done a number of really great articles---including one just this week on green designed homes.
posted by effluvia at 7:11 PM on June 29, 2011

Home Power has an online subscription (or a free sample copy) that's worthwhile. If you already have a utility feed, you're probably better looking at net metering rather than using batteries. Batteries are big, heavy and inefficient.

The big issue in the Caribbean is not the solar resource, but the environmental protection. High humidity and bugs will destroy even the best systems.
posted by scruss at 4:52 AM on June 30, 2011

I highly recommend solar. But depending on where you live, there are a lot of variables on installation, as well as how it will work with the local power company. I'm not familiar with how things go on the islands.

I had a system installed 18 months ago, in New Jersey, and it has significantly cut into my electric bill - upwards of 80%. That is not including the SREC program (which I imagine would not be available in the islands, but other rebates may be).

No batteries. they reduce the efficiency too much, and require too much maintenance as others have discussed. Pumping back into the grid lets you net-meter and spin your dial backwards (again, as long as it interfaces with your power company).

Because you are messing with the direct electrical to your house, and the power company's meter, you should get it professionally installed unless you are an electrical wonk.
posted by rich at 6:59 AM on June 30, 2011

LWTG: Isn't the partial shading issue resolved with micro-inverters, which seem to be standard these days?

Well that is certainly one of the main value propositions of micro-inverters. Shading is still bad, but you only lose the shaded panel not a whole string of 10 or more panels. But while they are an up and coming technology I don't think they're anything close to a standard yet. I think the vast majority of residential installations are still using central inverters so shading and general placement of the array will have a big impact on energy generation.
posted by Long Way To Go at 7:52 PM on June 30, 2011

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