### Home Made Energy: Renewable Energy For The Rest Of Us

Google Chrome's ad blocking is unfortunately not as good as Firefox's, so occasionally I see ads on the web. I generally ignore them, but I do click on the occasional one either because it's interesting or because I don't like it (since my clicks cost them money!). On The Straight Dope today I came across "Home Made Energy: Renewable Energy For The Rest Of Us". This company sells a guide which purports to tell you how to run your house purely off wind and solar power for less than $200. I'm skeptical. First of all, electricity costs something like twenty cents a kilowatt-hour, and they're talking about saving some hundreds of dollars a month. So let's say$100 a month - that's 500 kWh a month, or about 700 W. More credible sources cite about $10/watt for solar power, or$7000 for such a system. So is this guide really nonsense? Not necessarily.

Solar cells are expensive to make - think of making microchips the size of a solar panel. Not quite fair - they don't need the density of components, but they do need the extremely pure silicon and the high-vacuum manufacturing - but a sign that there's a good reason they aren't cheap. A solar system also needs some electronics for converting electricity to a useful voltage, and some way to deal with the fact that the amount of solar power varies in a way that has little to do with the demand for solar power.

I think a reasonable guide of this sort might be able to point readers at where to scavenge used or discarded parts for all of the above. The power electronics are definitely something a clever amateur could build out of scavenged parts (at some risk to their life!), but I think it would take incredible luck to obtain solar cells that worked and were that cheap. It's also possible that a guidebook could explain how to take advantages of government programs to encourage renewable energy, perhaps obtaining discounts or tax credits on the hardware.

The biggest way governments or energy companies could encourage renewable energy of this sort is to eliminate the need for energy storage. Since most of the people who'd be considering this sort of project already have a connection to the electricity grid, if the utility company is willing, you could simply sell them electricity whenever you make more than you need, and buy electricity when you need more than you buy.

Ideally, as a homeowner, you'd get paid the same price for the electricity you sell as you pay for the electricity you buy. Unfortunately, this is often not the case. There are good reasons electric companies would pay less for electricity they get from homeowners than they charge homeowners; for one thing, all those wires to distribute the electricity aren't free. More subtly, it's really difficult to store electricity on the scale that utility companies deal with, so they have to work quite hard to make sure that the amount of electricity fed into the grid in any given second exactly matches the electricity drawn out of it in that second. Having countless small generators outside their control is going to make that job much more difficult.

That said, persuading companies to act in a way that costs them money but benefits all people is a natural role of government. Paper mills have waste treatment systems not out of the goodness of their nonexistent hearts but because the government charges them massive fines or shuts them down if their effluent is too toxic. So if the government were to force (or fund) companies to pay consumers the same price for electricity they generate as they charge for electricity they use, suddenly a lot more small-scale power generation projects would become cost-effective.

Incidentally, another approach for storing solar power for when you need it is to let it charge your solar car (or plug-in hybrid). This has even been proposed as a scheme to help load-levelling in the power grid.

Anyway, the upshot of all this is that I think that yes, it is occasionally possible to scrounge together a cheap renewable energy system. But I suspect that the claimed $200 is only possible with in the best possible case - scavenged parts, government subsidies, living in a sunny desert, having a cooperative utility company, and incredible luck. #### 6 comments: Popup said... I think you're onto something here. It's commonly called 'Feed-In Tariff', and has been tried in Germany since ten years where it has enabled them to become a world leader in solar power. I don't know the details, but the idea was that the utilities would have to buy surplus renewable electricity at a fixed price determined by the federal government, based on the production costs rather than the volatile energy market. Similar schemes are also implemented in other countries, (at least according to the wikipedia article on the subject) On the list you also have Spain, Holland, China, parts of the Us and many Australian states. (Ooops, I thought you were in Australia, mainly because I came to your your blog from DansData. Turns out you're in Canada, right? (Apparently there are some similar schemes in Ontario)) FatBigot said... You assume that solar is the main technology. If you are trying to minimise costs and maximise scavaging, I' have thought that pico-hydo or wind would be better. In both cases the prime mover can be a standard 3-phase induction motor, used as a single phase generator. ( A capacitor on the other phase ensures sustained magnetisation). See http://www.eee.nottingham.ac.uk/picohydro/documents.html#manuals Popup said... The main problem with wind power is that it's extremely variable. Wind power goes as the third power of wind speed, and the wind varies considerably. (Unless you're in certain locations, e.g. such as those chosen for off-shore wind parks.) (Read this for an entertaining account of Tim Hunkins experiments with wind power) Solar power is much more reliable. Even when the sky is cloudy, the insolation is about 10% of a sunny day (Compare this with this.) On the other hand I agree that hydro is great. I live in Switzerland, but grew up in Sweden, two countries with about 50% hydro power. Once the dams have been built, the maintenance costs are low, and the environmental impact is negligible. Anne M. Archibald said... I should have said, first of all, that I'm not at all convinced that widespread small-scale generation is a good way to go about renewable energy, any more than it is for fossil fuel power generation (after all, many homeowners own gasoline-powered generators). But there are other reasons to argue for locally-generated power: emergency situations and as a way to reduce your carbon footprint without waiting for your power company. I know there are places that will buy power back from consumers; in fact one of my parents' neighbours in Nova Scotia has a wind generator that operates in this way. Unfortunately, he gets such a low price selling his electricity back to the grid that while it's marginally worth it for him to build enough to offset his electicity use (heating a swimming pool, in the event), it's just not worth it for him to have any more capacity. I didn't mention wind or pico hydro mostly to keep the post simple. But while anybody who owns their own home can stick some solar cells to the roof, fewer people can usefully build wind power systems, let alone hydro. The wind turbine I mention above is rated at 15 kW, and is a big, noisty structure on the crest of a hill, well away from the house. I don't think you could build a useful wind turbine unless you were in a rural area (that was windy). Pico hydro is of course even more selective; you basically need an adequate stream running across your land, which must have an adequate slope to it. Given that, in North America at least, only a tiny fraction of the population is rural, this severely limits the utility of such schemes. Even the suburbs don't hold that big a fraction of the population. How individual small-scale generation can be applied to help apartment dwellers like me I don't know. Perhaps solar on building roofs, although I suspect container gardens would be better. In all, I think I'd favour gigawatt-scale solar/wind/hydro farms stuck in suitable places (deserts, offshore, where they already are). All the more so if we move towards hydrogen or synthetic hydrocarbons as an energy carrier, so that variable energy sources can be used to generate fuel rather than feed the grid. FatBigot said... Sorry, I read the original article, but did not click through to the HomeMadeEnergy site. I thought it was less explicit about being solar, and I was trying to point out a source of information that did not require$200.

Distributed generation, either renewable or CHP really requires intelligent metering that only attempts to sell back to the grid when the supplier wants it to for capacity or network management reasons. It can dump spare energy into your hybrid car's battery or local water heating otherwise.

I do not know how tightly the US grid is kept at 60Hz. In the UK the deviation from the nominal 50Hz has been proposed as a way of signaling optional loads to shut down, but I suppose it could be used to signal a network feed-in requirement. See http://www.dynamicdemand.co.uk/grid.htm

I agree with the point about centralized sources; these are far easier to manage, and the only appropriate way to feed big loads. A good approach I find is to ask "How many of these windmills are required to power one commercial steel recycling furnace?"

Anne M. Archibald said...

The North American grid's 60 Hz is used as a time standard in (for example) cheap clocks and timers, but this is only a constraint on the number of cycles per (say) hour; in practice, looking at the interference we see in pulsar surveys, it's clear that there are plenty of two-minute chunks in which the nominal 60 Hz is off by quite a lot (0.1 Hz?). So in principle you could use it to signal small-scale generators. It would require a great deal of care, though, since it's necessary for all generators on the grid to remain exactly in phase to avoid uselessly shipping power back and forth across the grid. This is one of the subtler advantages of high-voltage DC distribution systems- they decouple the phase and frequency of the AC at their ends.