One of the great frustrations of residential solar power is that there does not seem to be a way to dip your toe in the water before going for a swim. What I mean is, wouldn't it be nice if you could install a small scale photovoltaic panel system and see how well it actually works over a month or so? I discovered a couple of years ago that when I called solar panel installers and wind generator installers here in Boise, none of them returned calls. Not one. (My guess is that they are all too busy doing installs--or worse, warranty work--to return my calls.)
One of the problems used to be was that there was a lot of capital investment in a traditional solar panel system. You needed a big inverter to convert the output from ten 215W panels into house current, and then the grid tie gadget to connect to your house. (The grid tie prevents current from the panels going back out over the grid in the event of a power failure, which would fry the electric company's workers, and also turns the meter backward when you are producing more power than you are using.) The cost of that inverter was, of course, substantial, so it would be very expensive to buy an inverter, and just one or two panels.
Microinverters should have changed this equation substantially. Microinverters convert the DC output from a single solar panel into AC. This lets you start out with one or two panels, and then scale up--perhaps buy two panels and two microinverters a year. At a minimum, it would let you find out if the initial installation was going to make sense before committing yourself to $20,000 of capital. (In addition, microinverters have the advantage that variations in output from solar panels can impair the total output of a conventional, string inverter; microinverters do not.)
It occurred to me that I have a small (35W) solar panel lying around the house, left over from my attempts a few years ago to find a way to turn a clever solar power idea of mine into a business. A 200W microinverter could easily take that panel and give me enough power to test whether it makes sense in my setting. But how do you connect the microinverter to the house? Again, you need an electrician who understands what is going on--and if I couldn't even get anyone to return my calls, what are the chances of getting someone to do an installation this simple (and therefore not very profitable)?
There has been some talk about microinverters that plug directly into your AC outlet, rather than requiring wiring through the breaker box. There are some downsides to this, however. One of them is the grid tie problem is still there: if the grid goes down, your solar panels are going to zap electric company workers who might be some distance from your house. The other is that if you have the output of multiple panels plugging into that outlet, it is going to be more current than the wiring can handle. I suppose you could plug each microinverter into a separate outlet, but then you have the problem that you have to be plugged into an outlet for every circuit in your house. Going to the mains for the house makes a lot more sense.
Anyway, it is a bit of a frustration. Someone needs to come up with an easy way to connect microinverters to the house, or there needs to be solar installers interested in doing small scale installs so that people like myself who are not primarily econuts can make sure that this makes sense before investing heavily.
UPDATE: I received a call back today. And the person who called me back has read my Cato Institute paper.
It may make sense to use the microinverters for a small (400W system) as an experiment, but you do need to go with a several thousand dollar hybrid inverter to get both net metering and either battery backup or the ability to sever yourself from the grid (as might be useful in the event of a long disruption of grid power). But if I decide after a few months of use that a 400W system is cost effective, or will be, then it might make sense to go big on a hybrid inverter, and start adding 800W a year of panels for a couple of years.
Well if the SCOTUS upholds Obamacare and Barry gets his second term we will all be told to buy a Volt and install solar panels!
ReplyDeleteOne of your worries may not actually be a problem. I work for a company that makes microinverters, and the MIs are required to shut down power production if the grid goes down. We have to wait five minutes after the grid comes back before the microinverter starts processing power again. This is precisely to solve the problem of zapping electrical workers, and it's done on a per-inverter basis so no special wiring is needed.
ReplyDeleteI have since figured this out--that the microinverters shut down when the grid side stops supplying power.
ReplyDeleteWhere I live it would be very useful if the solar panels continued providing power after the grid failed (even though this is usually at night, when solar power production drops reliably to zero anyway, and the backup generator would take over). This is mostly for the end of civilization as we know it scenario.
The real solution is for the microinverters to feed batteries, and have the batteries feed the mains. But I get the impression that only the string inverters are set up to do this.
To conduct your test, try this. Go to the breaker box and switch off one circuit. Then connect your solar system to that circuit, perhaps through an outlet.
ReplyDeleteClayton,
ReplyDeletethe problem, I think, is that the background of longtime solar people is in minimalism. If you look at the people in the 70s who were using solar panels, they were using a minimal amount of electricity, just enough to run a few 12-volt DC appliances and a handful of outlets. For them, a 200-400W setup was fine. That's certainly somewhat easy to dip your toes into; but integrating that into a standard wired house is a pain. What people would traditionally do is have a second wiring system. You could just run extension cords around to the places you want powered via the solar system, or you could also run a second system in the walls.
But it's not nearly as convenient, which I think is why you don't see it with regular people who already have a conventional house. Running a regular house that might use several KWh a day is really hard to start small with.
There's no question that reducing power consumption is the best strategy towards being completely independent. It just isn't terribly practical with an already built house. Realistically, if the end of civilization as we know it happened, then many of the devices that consume power in our house would become irrelevant: computers (because there would be no Internet service anymore); television (which is almost irrelevant already). Air conditioning would be recognized as an unneeded luxury. It would not take enormous power to keep the well pump, pressurization pump, furnace, microwaves, refrigerator, and a few lights running.
ReplyDeleteFor testing purposes, I'd just plug an appliance directly into the microinverter. Maybe a coffeepot, or an older computer or old TV. Check it with an ammeter, then do some calculations of your overall use. That should give you enough to decide whether to start investing thousands of dollars.
ReplyDeleteHere in the Bay Area, there's an outfit advertising that they'll install rooftop solar, and only bill you for your usage, at lower than PG&E rates. I haven't called them to find out the details, such as how long you're tied into a contract, or what happens if you sell the house, etc.
Small experiments like you want to do don't seem very useful compared to just sitting down, deciding your goals, and then doing the engineering and financial analysis.
ReplyDeleteWhat is your goal? It sounds like you're trying to kill two birds with one stone:
1) save money
2) improve the reliability of your power (grid down due to natural or man made causes)
The two are incompatible; you have to choose one or the other. Then you can proceed with your analysis to see if it is even feasible.
Actually, saving money is not my primary goal. My average electric bill is about $45 a month. I don't mind spending a little bit of money to have electricity that isn't dependent on the grid. I just don't want to put $20,000 into a system and have it never pay itself back. That would be crazy, since I consider social collapse a minor possibility.
ReplyDeleteSomeone mentioned that you need to choose between economic savings and reliability. If you want to improve your power reliability, solar is not the way to go. Unless you want to spend another $10-20m on battery backup, doubling your cost.
ReplyDeletePower outages are more likely to occur in the winter when there is little solar energy anyway. Think cloudy, short days and low sun angles.
So for the economics, it is easy to figure out. You say you pay $45/month for electric. Call it $600/yr. Bump it to $1000 to account for future increases in electric costs. I suspect yours will go down due to all the gas from Bakken but $1000 is a nice round number.
You said the cost of the system is $20m. Divide $20,000 by $1,000/yr and you find that it will take you 20 years just to break even.
That assumes, irrationally, that the solar cells does not (They do)and that no maintenance is ever required.
John Henry
Pngai said that saving money and increasing reliability are incompatible goals.
ReplyDeleteOften true but perhaps not for you.
Think about small scale cogeneration.
Cogeneration is the production of electricity and heat from the same source.
It is something, given your talents, that you could build yourself. That would save more money and give you a fun project to work on.
Get a 10KW (or whatever size you need for your house)generator. Preferably one that can run on natural gas (assuming that you have it available) and on gasoline or diesel (for when the gas is out)
Get one that is water cooled if you can.
Connect it to your household electric system with the appropriate backfeed and/or transfer system. Fire it up and start generating power.
So far, what you have is a fairly standard backup generator.
Now,get an exhaust heat exchanger. I think you can buy them at West Marine or other boating supply house. Connect it to the generator exhaust and Voila! you now have hot water that you can use for heating or for hot water.
You can get more heat from the radiator.
I don't know your house or size but the waste heat from 10KW would go a long way to heating a normal size house.
This also qualifies as alternative energy so you should get the same tax break as on solar/wind other alternative energy. (It used to, anyway. Under PURPA. Check to make sure it still does)
The reason this works economically is because your power company works under the laws of physics. Only about 30-40% of the energy input to any fossil fuel generation can be recovered to turn the generator shaft. Add another 5-10% for transmission losses and you can see all the utility energy that goes to waste.
Your system, assuming that you can use all the waste heat you recapture will run use 70-85% of the fuel energy input.
I was heavily involved in this back in the late 70's early 80's. Even considered becoming a dealer for a system based on a skid mounted 60HP Fiat engine/generator/heat recovery package.
I did purchase a 2 MW plant based on Diesels and Hitachi direct fired chillers in 84.
Let me know if you would like to discuss this further.
John Henry
Part of why I am getting an estimate is that I am a bit skeptical of this making economic sense by itself.
ReplyDeleteI am led to believe that battery backup (and the hybrid inverter required to allow both grid-tie and battery backup) is going to be several thousand dollars. Batteries, of course, have limited lifetimes, and will need replacing. If cost alone were a motivator, it would not make sense at all.
Where we are, we often get long sunny (although cold) winter days. Boise can be covered under a layer of fog, and yet the sky where we are will be completely clear. Low sun angle is a problem, along with shorter days, although slightly compensated by greater efficiency of photovoltaics at lower temperatures.
We have a backup generator already, so solar is not going to be the only defense against loss of grid.
I am counting on photovoltaics getting cheaper over time--they have already dropped substantially in price over the last two or three years. Now, if only the Chinese government continues its supposed foreign aid program of subsidizing manufacturing....
I was talking about how "saving money and increasing reliability" are incompatible goals with solar.
ReplyDeleteThere are two big problems:
1) solar by itself, even in CA with more sun and much higher electricity rates, takes a long time to pay off and that's ignoring the cost of capital
2) solar is not reliable, if you want reliable, you must invest even more money on batteries (with their maintenance and life cycle issues)
Cogen is a far different animal and in winter, seems like a very attractive concept if you have good access to natural gas.
We have LP gas in a tank, but there's no natural gas supply for at least 20 miles.
ReplyDelete