Circuit protection can be an important element in designing a solar power system. This is particularly true if you’re putting together an off-grid or battery-based power system.

It’s not such an issue if your system is hard-wired into your electrical panel, but in this case you’ll need to have a qualified electrician do your installation, so follow whatever they say.

But a battery-based system really needs fuses or circuit breakers. You might think that since you have 12 volt batteries in your car that they’re not dangerous. The truth is that a short or overcurrent can deliver thousands of amperes of current into a fault, depending on the size of the battery array.

A fuse is a little device that fails if there’s too much power going through the circuit. This provides a basic level of protection, but you need to replace the fuse if it blows. Sometimes people take shortcuts and just patch across where the fuse was with a piece of wire. This defeats the purpose and makes the installation more dangerous.

A circuit breaker is a much better piece of equipment, because it can be reset once it trips. But you have to be sure to buy DC rated breakers, not AC breakers, because they handle current differently.

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If you live in an area where you pay different rates for electricity depending how much you use, solar panels can be a great way to to shave your costs without cutting your electricity bill entirely.

All you need is a simple grid-tied system that offsets your usage in the most expensive energy time, which is probably the “last” energy you use. This is the electricity that costs the most per kilowatt hour.

I’ll be back with some sample systems and a simple calculation.

Read more on this at the blog at gogreensolar (click the banner in the right column, then go to blog).

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There’s an interesting post at civilianism.com about solar panels in roads, but sadly, I don’t think it’s going to happen. The theory here is that every major roadway in the country could be turned into a big solar panel, along with transmission lines embedded in the pavement.

Another example of excitement without a basis in reality?

Well, it’s not as bad as the claims that you can generate all the power you need to erase your utility bill with a simple solar panel that you can build yourself…

On the face of it, it’s an interesting idea. Certainly roads provide a lot of surface area. But the technical challenges are big. More than that, the funding challenges are huge. Where is the money going to come from to rip up perfectly good roads and install solar panels, not to mention all the infrastructure to transmit the power?

Fact is, it makes a lot of sense to generate power where we need it, which is on our homes and businesses. It also makes sense to generate it close to where we use it.

As for the road project, the Department of Transportation has invested some money in a pilot project, which would seem to imply some legitimacy. However, the amount of the grant is just $100,000. A quick search for how much it costs to install a mile of interstate gave me a figure of (average) $20.6 Million (source: http://www-pam.usc.edu/volume2/v2i1a3s2.html). I think this amount is just someone covering their a**.

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A lot of people who are thinking of installing solar panels do so with the hope that they can take care of all their electricity needs. For many of us, heating our spaces is one of our biggest uses of electricity.

Well, here’s the bad news.

Solar electric power is a TERRIBLE way to heat space or run a space heater.

Here’s why: First you have to turn solar radiation into electrical energy, then store it in batteries. Then you have to take it out of the batteries and turn it into high-drain power to heat an electrical coil to create heat. Every step of this process has inefficies. By the time you add it all up, you would need a huge bank of panels and batteries to provide the kind of power you need to heat your workshop with solar power.

So if that’s what you want to do, think again.

On the other hand, you can definitely use solar power to heat things. But you don’t bother with the step of turning it into electricity.

Solar hot water heaters are among the most efficient and most affordable solar power systems. The paybacks are much faster than with PV panels and batteries.

A solar hot water system consists of collectors on your roof that capture HEAT from the sun, not electricity. The heat is stored in water or some other solution, and is then transferred to water for domestic use. You can shower with it or pump it through your radiators.

Solar power isn't good for space heaters

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DIY solar panel kits and instructions are a great idea, but if you don’t understand the basics of solar energy generation you’re going to be disappointed with what you get.

For example, let’s take a look at how one company, GreenDIYenergy, sells its product.

The basic idea here is that they’re hoping you get so excited about the idea of generating “practically free” power that you won’t pay attention to what they’re actually promising. Which isn’t as much as they’d like you to think.

The sales page starts with a typical persuasion technique: make you think the alternative is really expensive.

A few years ago I started looking into solar energy. Just like you, I started with an online search on how I could save money with solar electricity.

I was shocked to see how much it cost to have solar panels installed at my house. The estimate I got was over $35,000 and the pay back time for that was just way too long. I didn’t have that kind of money, not even close. I was resigned to the idea of paying the electric company each and every month until I met a friend who had a solution. My friend explained that he was building his own solar panels and for just a fraction of the cost of new retail solar panels.

The author has anchored the price in your mind at $35K. By this time you’ve already read the headline that says you can build a solar panel for less than $200.

But he doesn’t say how many panels were included in that bid. There are two things to consider here. One is that the cost quoted was for the entire system, including the necessary equipment to put the panels on the roof and connect the system to the electrical grid, and it included installation. Probably $20,000 of that was for panels and the rest was for labor and other equipment.

At an estimated $7 per Watt (prices are actually lower than this now), $20K of panels should be 2,800 Watts of potential power.

The panels described in this project turn out about 100 Watts, so you need 28 panels at $200 each. Cool. That’s only $5,600. Much cheaper than $20K.

But it doesn’t include the value of your time. One free guide to building solar panels estimates it takes 12 hours to put together a panel (a lot of this is soldering the cells together). 12 times 28 is 336, or 8.4 40-hour work weeks.

I don’t know about you, but I think that’s a whole lot of time. What’s your time worth? Everyone is different, but let’s call it $15. Because if you went out and worked instead of tinkering with 28 solar panels, you’d get paid that much. That’s $5,040. Could be a lot more if you get paid well.

So now we’re up to $10,640, or about half the cost.

And yes, it’s absolutely true that this is “a fraction” of the cost you’d pay retail. 1/2 is a fraction. So is 4/5 or 9/10.

Of course, there are many ways to think about your time. For example, you could flip this all around. Let’s say you’re willing to spend $35,000 on a complete solar power system. You can make the panels for half price (even though it will take over a year of working 5 hours per weekend) and if you buy the necessary electronics at a discount and build and assemble your racks and wiring yourself, you could do that for half price as well. So you might be able to have a complete system put together for $17.5K instead of $35. It’s possible to convince yourself that you’re actually MAKING $17.5K by building your system yourself.

Now, I’m not sure I’d go that far. Please tell me your thoughts in the comments.

Oh, and please don’t make plans based on the numbers I’ve shared here. They’re just ballpark estimates. You’ll need to do your own research to figure out what’s true for you.

Check out green diy energy. I’ll be posting more about their sales letter (which actually makes some great points) in future posts.

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Tile roofs are one of the hardest places to install solar panels. A company in California, SRS Energy, has come up with an innovative system of interlocking tiles that are designed to be installed with another popular brand of real tiles.

The tile panels are made from a lightweight performance polymer with a solar film attached to them. They hook together in a “plug and play” fashion, so regular tile roof installers can be trained in installing them pretty easily.

According to the manufacturer, “SRS Energy rigorously tests the Solé Power Tile™ under harsh conditions for durability, including long-term UV stability, color fastness, wind resistance, electrical output, safety, and extreme mechanical stresses. The tiles ship, stock, and install just like traditional roofing, but are even lighter than their ceramic counterparts.”

The panels generate 500 Watts per 100 square feet. That’s a 10′ by 10′ area, in case you don’t feel like doing the math yourself just now.

It’s not clear how much they cost per Watt. It can’t be as cheap as regular solar panels, but then again, the tiles are doing double-duty as your actual roof, so the payback period could be faster than if you tried to install regular solar panels over a tile roof.

solar panel tiles installed on a roof

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I just read a post on someone else’s blog that I suspect was written by a hired writer who didn’t know much about solar power.

They went about it in an interesting way.

First they looked up how much solar energy strikes the earth, in terms of energy per square meter. Then they adjusted this for average hours of direct sun (assuming the panels to be installed weren’t on a tracking system). Then they chose an average efficiency for solar panels of 10% and arrived at an amount of power available per square meter of solar panels on your roof.

Their base calculations relied on an average of 1kW of power used in the house, with peaks of up to 3kW. In the end they came up with a figure of 80 square meters of panels required.

To me the entire calculation seemed backwards, and much more complicated than it needs to be.

Solar panels are sold in standard sizes with specific Watt ratings. I.e., you can buy a 100 Watt panel, or a 160 Watt panel, or even a 200 Watt panel. (This is nominal output, of course. There’s some inefficiency in the wiring and other electronics, and they won’t work that well if they’re dirty.)

Why bother to go through the whole calculation of how much solar energy falls on the earth? What we want to know is how much can we generate with commonly available panels. We’re practical, not theoretical.

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Sanyo has come out with a new portable solar panel. It’s called the Sanyo Eneloop Portable Solar. It’s a little bigger than a regular book, and can go with you anywhere.

All you have to do is unfold it in a sunny spot and plug your gadgets in.

An hour of sun should charge up your phone for a 40-minute phone call.

Details are a little scarce on this product as it hasn’t been released yet. It’s coming August 8.

Portable solar panel

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Solar panels get dirty. You’ll have to clean them if you want to be able to generate all the solar power you need.

George over at Practical Environmentalist has a great post on how to clean solar panels. The basic idea is to make sure your panels are in good shape (no cracks in the glass, etc) and then it’s pretty much as simple as cleaning a window. Check out the post for full details.

Dirty solar panels in Nevada

Photo courtesy of naturalturn on flickr.

That much dust can show up in one sandstorm, and there’s not much rain to wash it away.

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When solar panels get dirty, they become a lot less efficient.

Google just did a study of their own solar panels (they’ve got a lot installed on their roofs). They compared the efficiency of the flat solar panels versus the ones that were installed at an angle.

Guess what? The flat solar panels had a lot of dirt on them. The sloped ones did not (except in the corners).

After the flat ones were cleaned, power output doubled. These panels had not been cleaned for 15 months. Read that again. The power output was cut in half from dust accumulation.

There was also dust on the angled solar panels, but just in the corners. So the efficiency gains from cleaning them weren’t as great.

Google now has plans to do regular cleaning of their flat panels.

What does this mean for you?

If you have solar panels installed flat on your roof, you need to get up there and clean them regularly. Probably every few months is good, though you’ll need to pay attention to any seasonal effects such as high pollen.

If you haven’t yet installed solar panels, this information should lead you toward installing them at an angle so that rainfall can wash them clean. This will save you a lot of maintenance time, and will keep your power generation at maximum efficiency.

Dirty solar panels at Google headquarters

You can get a link to the original google blog post at goodcleantech.

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