bolson: (Default)
The Porter Square strip mall has a strip of solar panels along the facade, but as shown in that Google Maps aerial view, most of the roof is not covered with solar panels.
What if it was covered with solar panels? Rough measurement from that map says the roof is roughly a rectangle 600ft by 87ft. Wider in some places, probably obstructed in others, I'll go with that and say its 52200 sq ft. Multiply that by the cosine of 40 degrees to account for the amonut of roof shaded by a tilted panel. 39987. There's a rather economical Kyocera KD235GX panel which puts out 13.35 watts per square foot. (13 * 39987) = 519831 watts of peak power. Half a megawatt! I heard on the radio that the biggest solar installation in Massachussetts is two-point-something megawatts.
With big flat roofs like these covered in solar we could have substantial generation in our cities. No transmission losses. No new transmission capacity to build. I think the economics for it are almost here, and they would be if we taxed pollution properly.

(yeah, I posted about that solar facade in Porter square before)
bolson: (Default)
Sometimes I think it would be cool to work on making windmills for cheap sustainable energy generation. The part of this it seems to make sense to me to start tinkering with this is alternator design. I finally bought an oscilloscope (USB oscilloscope, software display, Linux/Mac friendly) so that I could measure my progress. It came today, and I measured what I get from waving the magnets I have past a coil of wire I wound, and I'm barely above the background noise 60Hz hum that my coil seems very adept at picking up. Boo. But, thanks to getting my high school physics refreshed at Khan Academy, I know that the energy generated is proportional to ((the length of wire exposed to magnetic field) * (the strength of the magnetic field) * (the speed of the wire moving through the field)). So, there are the things to scale up. Onward!
bolson: (Default)
Look at this aerial view of the Porter Square mall. Look at the thin strip of solar panels along the front edge of the building, now look at the vast expanse of roof not covered by solar panels. That's the difference between solar panels being a popular thing that can be used for a little "greenwashing", and solar panels being an actually good economic idea. If solar panels paid for themselves and were profitable (and profitable at a better rate than basic conservative investments like bond funds), every roof would be covered in them. We're not there yet, I want us to be. I want solar to be cheap and effective and I want Coal and Natural Gas taxed to offset their externalities.
bolson: (Default)
To much fanfare, Medford installs a wind turbine at a public school.
http://www.boston.com/yourtown/news/medford/2009/07/mcglynn_school_turbine_right_o.html
Total cost of project was $645000

http://www.boston.com/lifestyle/green/greenblog/2009/07/medfords_own_wind_turbine_save.html
"A highly touted wind turbine at McGlynn Middle School in Medford has produced over 38,000 kilowatt hours of electricity since January, saving the city about $5,400, according to estimates from the Medford Clean Energy Committee."

$5400 in six months. $10800 in a year.
$645000*0.04 = $25800.00

The money would have been better spent by putting it in a bank.

And yet, clean sustainable energy is something we absolutely must do, we just need to bring the cost down I guess. (And tax the externalities of that damn cheating coal.)
bolson: (Default)
I keep running the numbers and coming up with the conclusion that buying my own renewable power generation (most likely solar) doesn't actually make economic sense. I could do better sticking the money in a bank.

Let's say I buy a $20,000 solar system and it will last 20 years and then be useless and need replacing (it's not quite that bad, but I think this is a reasonable simplification). In those 20 years the solar system needs to generate enough electricity to pay for itself and whatever I could have gotten if I'd invested those $20,000 instead of buying the system. I'll assume I could have gotten 5% return on investment. So, 20000 * (1.05^20) = $53066. Electricity I buy costs me $0.20 per kilowatt-hour. The $20000 solar system needs to generate 265330 kWh over 20 years, or 13266 kWh per year, or 1105.5 kWh per month (I don't use that much), or 36 kWh per day. The per day number is interesting because I once looked up and found that Massachusetts gets an average of 4 hours of full sun equivalent sunlight per day (noon is full sun, off that and cloudy times are less). To get 36 kWh per day out of 4 hours of sun I need 9 kW of panels on my roof. I checked one online solar vendor and it looks like 9 kW of panels would cost a bit over $40000, and that's without installation and support equipment like the grid-tie inverter.

I did some algebra on the above calculation and came up with the equation below.
Solar feasibility calculation:
dollars per installed kWh <= (lifespan in years) * (price of electricity in dollars per kWh) * (daily sun hours) * 365.24 / ((rate of return) ^ (lifespan in years))
For 5% (1.05) return and $.20/kWh and 4 hours of sun a day over 20 years, installed solar power generation needs to be at less than $2202 per kilowatt of capacity.

On a personal basis, there may be subsidy programs that cut the cost of a system enough to make it worth doing. It's only a factor of two or three away from being naturally profitable. I also like to contend that 'cheap' power from coal is cheating and its cost should be much higher and a Carbon Tax would help even the score. This is equivalent to saying that if the cost of electricity doubled, buying your own solar generation would be worthwhile.

I suppose the general form of this is:
if [expected value of generation over life of system] >= [expected return on investment of system costs]
then: buy the system.
Now I'm imagining more complex models that project the cost of power over the next 20 years. Maybe I'll work that out another time.
bolson: (Default)
Dear Dr Lj,
My old house is cold and heated by expensive oil, I believe the best course of action is to improve its insulation. Blowing in insulating fluff into the attic seems like it should be an easy win. I hear this can be done to the walls too, but is somewhat more involved as it may include peeling off parts of the siding and cutting holes to blow in through. I just had another thought, take off all the siding and add a few inches of insulative thickness to all the outer walls. This of course seems like a somewhat radical measure. Any ideas on if this is otherwise a reasonable idea? Anyone else heard of this or other thins being done?
bolson: (Default)
But something like this electric thing is still kinda appealing to me. It would get some serious consideration if I needed to acquire transport for a regular commute that didn't fit bicycle, train or bus routes.
bolson: (Default)
What's the biggest thing I can do to make my household more energy
efficient? Insulate it. Well, that's expensive and hard (but totally on the
to-do list for next season if not this).So, what's the next big thing that
we all get reminded to do? Change lightbulbs. It's easy and cheapish and
relatively effective for that amount of work. So, I took stock and I have
over 40 lightbulbs I could replace. Half of those have a
smaller-than-standard socket as part of some decorative fixture in the
ceiling fan. Another quarter are much shorter than common bulbs. Between
these constraints my choice in CFL replacements will be somewhat limited,
but I'm pretty sure I've seen the right kinds of things out there.
bolson: (Default)
"When demand for oil and coal increases, their price goes up. When demand for solar cells increases, the price often comes down." - Al Gore, 2008-07-17


http://www.epa.gov/oms/rfgecon.htm says:
113500 BTU per gallon of gasoline

1 BTU = .293 watt hour
1 gallon of gasoline = 113500 BTU = 33.26 KWh

My electric last bill came out to: $.21 / KWh
$6.98 per gallon of gas in electric equivalent.

Except that car engines are terribly inefficient and relatively little of the BTU heat energy of gasoline is actually used in motion. Batteries and electric motors are probably much more efficient (but I don't have a good guess really how much).

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