I've just been talking to a friend about what my house will be like when I'm "all grown up". Here's an excerpt:
Michael: I want a house so I can have a roof for solar panels, a garden for a heat pump, a big garden for a wind turbine, A STREAM! I also want a weather station.
It's not as stupid as it sounds: one day I would like to be energy self-sufficient (if not supplying energy to the grid), and residential solar energy is an excellent way of achieving that.
Solar energy is a versatile form of energy; it can provide both heating and hot water, as well as electricity. All you need is the space (and money) to put up the solar panels.
Types of residential solar energy
A house with solar panels. Photo courtesy of Sare-Bear
You can either get solar photovoltaic panels to generate electricity or solar thermal panels to heat water.
You can also cleverly design your house (if you are building it) such that the sun heats it entirely. This is known as passive solar heating.
Passive heating involves designing your home in such a way so as to use the sun to provide heating and cooling just by the movement of air around it.
Take a look at solar electricity for homes from www.green-energy-efficient-homes.com as well, for a more hands-on approach.
Should you invest in residential solar energy?
This depends on many factors. Where do you live? How much space do you have? Are you overshadowed by trees or other buildings? Which way would the panels be facing? Do you have the financing available now? Let me talk about each one by one.
Location, location, location
As you are probably aware from experience, energy from the sun gets more intense as you get closer to the equator.
This is due to the Earth being curved; the same amount of energy from the sun is spread over a greater area due to the curvature of the Earth as you move further from the equator.
This map shows the average surface solar energy density (energy per metre area) around the world.
Natural resource - solar power (potential) http://maps.grida.no/go/graphic/natural-resource-solar-power-potential
The equator is not actually the best place for solar power as there tends to be quite a lot of cloud cover. The best regions, as you can see roughly on the map, lie between 15° to 30° north and south of the equator.
Another house featuring residential solar energy! Photo courtesy of Adam Fagen
Does this mean that if you live in North America, you should not consider residential solar power?
No; it means that someone in Texas with solar panels will, on average, receive more energy than the same sized panels in Canada.
Let me give you an example. Here in London, UK, today [23/02/09] at 11:47, the highest solar radiation was 213 Watts per square metre. (Source: the weather station atop the physics department at Imperial College London)
If I had a one square metre solar panel on a roof, that is the most it could ever generate: that said, though, solar photovoltaic panels are not 100% efficient; they don't convert all the incident solar energy to electricity.
I think the best is around 45% and that is in a lab somewhere, so even liberally let's assume 30%. So today, at peak solar radiation, I'd have generated no more than 64W, proably much less with commercial systems.
That's not even enough to power my laptop, I'm afraid, and 1 square metre is hardly small. You would have a much larger area than that if you were to install solar panels on a roof.
Remember that this number rises a lot on a sunny day, especially in the summer. I'll report back on a sunny day in June!
[Better late than never: on 11/08/2009 (that's August, not November), the peak solar radiation was about 740 Watts per square metre. I should stress that "peak", by definition, occurs only once, and that the average of the entire day would also be significantly smaller.]
Solar panels on the roof of an apartment block in California. Photo courtesy of kqedquest
Look at the map above and note that Texas receives a much higher energy density than London. As you can see, the use of residential solar energy depends on where you are, so the closer to the equator you are, the more excited you should be about the idea. It is not for everyone though.
emember also that the angle of the panels, the direction they face, and any shadows on them will affect how much energy they generate. North facing panels in the northern hemisphere wouldn't be sensible, for example.
Cost of residential solar energy
Solar panels don't have to go on a roof. If you have a big enough garden, they're just as good there - just make sure they're not overshadowed like one of these! Photo courtesy of R Walker
Residential solar energy is not cheap. That said, it would be considered a very wise investment for your home.
Solar panels would increase the value of your home, as once they are up, they just sit there generating electricity. A buyer would then expect much lower fuel costs, and that would be reflected in your house price.
Depending on where you live and how large your system is, it may take upwards of ten years for your panels to pay for themselves, but after that your energy is free.
This will only improve as solar technology becomes more efficient, cheaper, and more widely available.
It is still a bit of a specialist field. I know researchers in my department working on highly efficient solar cells, as well as less efficient cells which can be printed en masse on practically anything.
Imagine if the paint you put on the side of your house converted the sun's energy into electricity. Amazing.
A large building with solar PV tiles (right) and solar thermal panels (left). Photo courtesy of John Hritz
Solar roof tiles
What is the current state of your roof? Does it need replacing anyway? If so, you might be interested in solar roof tiles. Rather then replacing your existing roof tiles, you can get tiles that are themselves little solar panels.
That way, you don't need to add solar panels on afterwards, and they don't cost much more than regular roof tiles.
Benefits of residential solar energy
Aesthetics
The panels are likely to be on your roof, which means you will never see them. Neither are any neighbours who may complain about them being an eyesore.
Not only that but they are also silent. Contrast that with a wind turbine and there is an advantage right there.
Increasing the value of your home
This solar PV roof installation provides 5kW of electricity, providing 100% of needs, and they sell electricity to the grid in summer! Photo courtesy of Bob Gaffney
Which house would you rather buy - the one with high fuel bills or the one which generates its own power?
The promise of low utility bills is an attractive one these days, and a residential solar power system would certainly make your home more valuable to buyers.
I would love to see every new build to come with solar tiles as standard. There should also be grants available for you from your local government to support renewable energy technologies.
Check them out and you could save a sizable chunk from your costs.
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