Residential Solar vs. Large-Scale Wind Turbine

Factual Questions
1

(This will end up, I hope, with a factual question)

We are having a debate in our town right now on the merits of residential solar energy generation. The pro-solar people want subsidies from the rest of the rate-payers to offset the cost. Arguments are along the lines of “once installed it’s free, it eliminates fossil fuel usage, the more we install the less it’ll cost, etc.”

There are a lot of people who don’t want to subsidize the few pro-solar people, and the Light Department claims that we’d be better off investing the same funds in buying Wind-Turbine Power from “the grid.”

I did some calculations that here in Massachusetts even if we put solar energy systems on every single-family residence that was properly located/aligned it would still only generate enough KWH over a year to cover about 4% of the total state usage. Now I know that’s 4% of a really big number, but its still doesn’t make a big dent in our fossil fuel usage.

Does anyone have figures that would show an investment in large-scale Wind-Turbine generation would be more practical (or not) than a lot of small-scale solar installations.

Please note I am not talking about large-scale commercial solar installations or installations on large multi-unit dwellings; just typical single-family homes.

2

Why not do both?

3

Mind showing your work on this one? I’m curious.

4

This isn’t really a theoretical question, but a mathematical one, dependent on regional pricing, resource availability, and potential CO2-equivalent savings. You can’t just ask “Is solar or wind better/cheaper?” without the specifics. How big are the respective projects? How much do they cost? How much sun do you get? How much wind? Etc.

And then you get into the nitty-gritty like who takes care of aging inverters, who builds new transmission lines (and where), who are going to NIMBY your green asses, etc.

If you want an example, our county recently did a strategic analysis for renewable energy, comparing different potential generation and conservation methods against each other:

You’ll need something with that sort of depth and number-crunching, specifically for your region, to make any sort of useful comparison.

5

(With just a smidge of rounding-off for simplicity)

1,370,000; Single-family residences in MA
685,000; Capable of generating solar (due to orientation, light blockage, etc.)
3MWh/yr; Amount generated by one home (at least one tricked-out home here does that)
2,055,000 MWh; amount that could be generated by single family homes /year
55,000,000 MWh; Total electric usage in MA last year
4%; Amount that could have been covered by single family home generation

My assumption that half of homes wouldn’t be suitable for solar is arguable. On the other hand how likely is it we could get all eligible people to install solar? Our town couldn’t even get a majority to vote for a tax over-ride for road repairs.

6

Try this calculator : http://pvwatts.nrel.gov/

I’ve used it for an example house in Texas, and at least in Texas, it produces enough power to run the house and 3 others in theory. You would have to have complete panel coverage, which is less efficient for the relatively inexpensive panels, but you could skimp on inverter capacity.

7

Thanks. I guess I have a bunch of follow-up questions, but I’m not sure if you have the answers. These are the top-line ones:

  1. Where did you get the number of single-family residences?
  2. Where did you get the number of residences capable of generating solar?
  3. How much roof space is that assuming is covered with panels?
  4. How efficient are those panels assumed to be?
  5. What are the assumptions around solar insolance?
  6. How does power generation change seasonally?
8

I’m not the OP, but you can do this with public GIS data. For example, for rooftop space, you can get datasets like this one, overlay it with maps of residential zoning, and then sum up all the available roof space. You could also do cruder estimates with census data, which would give you # of households but not rooftop space, for example.

Insolation data is actually very well mapped for the USA, and you can use solar maps or zipcode/long-lat based calulators to estimate available sun, through all the seasons, for any given location.

Panel efficiency, inverter performance, degradation over time, etc. can all be estimated with online calculators or free software. Most solar installers will do the math for you as well, and give you an estimated payback time, upfront cost, maintenance forecasts, etc.

There are similar resources available for wind (wind maps, zoning maps, etc.).

9

I’d go with the solar panels.

Wind turbines only work when the wind is blowing at a certain rate and their are alot of issues dealing with where to put them. Basically all the good places already have houses on them.

Thing is our electrical needs are going to keep going up as more and more people turn to electric cars. Neither solar or wind will be enough.

10

[QUOTE=Urbanredneck]
I’d go with the solar panels.

Wind turbines only work when the wind is blowing at a certain rate and their are alot of issues dealing with where to put them. Basically all the good places already have houses on them.

[/QUOTE]

Another factor is that big mechanical things need regular maintenance. Bearings and gears need lubrication, the blades need inspection so they don’t fly apart, bolts need tightening, etc. Home solar’s maintenance needs are more along the line of keeping leaves off the panels.

Also, solar works wherever it’s sunny, which is almost anywhere. Even in foggy San Francisco, there’s enough sunlight to make residential solar a viable option.

11

You guys should look into Community Choice Aggregation, by the way:

http://apps3.eere.energy.gov/greenpower/markets/community_choice.shtml

Building individual solar units is arguably less efficient, with a greater payback time, than buying from a shared greener grid. If only because your community as a whole uses more power more steadily than any one household, unless you’re all growing weed or some such (which is where the residential solar cost savings in our county comes from).

12

The coal industry here claims that further wind development will not reduce coal use and gas use - because coping with the variations in wind power takes just as much power as leaving the coal generators running full time.

Or sort of – that’s a suggested end point, not the current state of the industry.

But it has the advantage of not requiring changes to the distribution system.

The big advantage to Solar around here is that the solar generation peak co-incides with the (start of ) the air-conditioning-demand peak. At best, this means lower peak demands at the generator, and on the distribution system. At worst, it means the voltage in all the surrounding houses going up, because the voltage regulation system is designed to keep the voltage up when there is a lot of local demand, not designed to keep the voltage down when there is a lot of local supply.

Overall, I’d say that, around here, there isn’t enough wind generation to be a big problem, and there is enough residential solar to start to be a problem in some areas.

If your light-and-power company is suggesting buying wind power, they’ve already accepted that you are going to pay more for your power, and they are suggesting that, in your area, they aren’t expecting to see a peak-demand benefit from solar.

No easy answer – at present, residential solar might be justified in some areas because of the peak demand benefit. As you’ve suggested, total demand is less relevant. You’d need more analysis to judge.

As for wind, I’ve never seen a report of a price benefit compared to coal, but it may have a price benefit compared to residential solar for you – no reason to disbelieve the numbers. At high percentage, it may not have much environmental benefit – but it’s hard to say where that number will lie, because those numbers aren’t finalised.

Any way, the actual numbers will depend on your local demand and supply situation

13

This is actually a fairly big deal – pretty much worldwide-- because without solar, you’d need lots of stand-by generators that only kick in at the peak demand. And right now the only real way to do that is to have them be fossil-fuel fired generators. So even if there was lots of baseline hydro or wind, you’d still be burning lots of natural gas to keep up during hot days.
But with solar, you need much less of that.