More on Electrical Usage

According to recent postings on Cleantechnica.com, large wind turbines need to generate about 3kW to supply a home (a planned wind farm in KS has a capacity of 250MW and will satisfy the needs of 85,000 homes). A small rooftop turbine works out to 6 kW/home, due to the lesser efficiency of smaller blades. The small rooftop model seems terribly expensive ($6.70 per kW), so I'll stick with the 3 kW/home number.

They also state that the average home uses 670 kWh/mo, which is 70% higher than our usage (see yesterday). This means almost 800,000 homes could be served with a 1000 MW coal plant.

Electricity per month

We use about 400 kWh per month. A 1000 MW coal plant produces about 520 million kWh/per month (70% time on line, which amounts to about 1.3 million homes supplied if they are all like us). I expect (need to check) that our usage is below average and that the estimate that a 1000 MW coal plant can supply one million homes is not far off.

Coal vs. Wind

I'm having a problem sorting out relative efficiencies of various electricity generation methods. For example, a 1000 MW coal plant is supposed to provide enough electricity for 1 million homes (this may be high, but I don't have good numbers). The power is then about 1kW/home. But only about 1/3 of the chemical energy of coal is converted to electricity.

Wind turbines need about 3 kW/home. So the efficiency of harnessing wind to produce electricity is in the same ball park as the efficiency for coal.

More Solar Economics Data

There was a report in Sunday's Columbus Dispatch about a solar home with a claimed 10-12 year payback. The owner paid $41,500 and received State and Federal grants reducing that to $21,500. He has net metering.

In his best month, he generated 806 kWh, which provides 115,200 kWh over 12 years. At $0.10.kWh, this comes out to around $11,000 worth of electricity produced - I don't see how he can break even.

Refs:

"Solar power users amass savings by folllowing the sun", Columbus Dispatch, 08 Oct. 2008

Stowell web page:

Energy Contest

Earlier this year I tried to get an energy conservation contest organized by a local group called Sustainable Grandview Heights. It was discouraging that nobody else in the organization was willing to pee a drop. Here are the Official Rules, in case someone else want to try:

"We are looking to reward the best energy savers in the Grandview Heights area. Since our scoring system allows small users to compete evenly with large users, everyone has an equal chance.

"How it works There are two contests: electricity usage and natural gas usage. Contestants can enter one or both contests.

"Electricity Find the item “Total Usage (Past 12 Months)”near the end of your most recent electricity bill (July or August 2008). Then find the same item on an earlier bill (January 2007 to July 2008). Record the numbers and mail to Al Rosenfield al.sustain@sbcglobal.net

"Example:
"August 2007 through July 2008 – 3071 kWh
"February 2007 through Jan 2008 — 3116 kWh

"Gas The procedure is the same, except that the number showing twelve-month usage is located at the bottom of the right-hand column on your bill.

"Example:
"September 2007 through August 2008 - 4868 Ccf
"June 2006 through May 2007 - 4985 Ccf

"All entries are due on August 31, 2008.

"Who is eligible To enter the contest you must pay an electric or gas bill for an address in the Grandview area, which means between the Olentangy and Scioto Rivers. The northern boundary is addresses on W. Fifth Ave. Everyone is free to enter - individuals, businesses, industries, and government.

"Judging The winners will be the contestants with the largest percentage decreases in usage. Here is an example of how it will work for gas:

"Contestant A Contestant B
"Aug 2007 through July 2008 – 4850 Ccf Sep 2007 through Aug 2008 – 1951 Ccf
"Feb 2007 through Jan 2008 — 5010 Ccf Nov 2006 through Oct. 2007 – 2057 Ccf

"Difference = - 160 Ccf (3.2 % of 5010) - 106 kWh (5.2 % of 2057)

"Contestant B wins because he made the effort to cut his usage by a bigger percentage, even though Contestant A saved more gas.

"There are two other requirements for winners to qualify. They must provide the judges with copies of their bills and an explanation of what they did to save energy. The judges can disqualify a winner if the saving is based on some unusual circumstances (got a programable thermostat is good, closed the house and went to Florida for the Winter disqualifies).

"?Prizes List needed.

"Any Questions Contact Al Rosenfield "

Solar in AZ

There’s an article from Lake Havasu AZ (08/21/08) about a church which installed a solar roof. It cost $100K and they expect to save $20K per year. It helps that they can get various rebates. One point is that the church is only heavily used one day a week and can sell a lot of the electricity that they generate to the grid.

The article also mentions that the average residential installation in AZ is 4 to 7 kW and costs about $8/W. The church cost was slightly less ($7.14/W for 14kW), suggesting that the cost benefit scales only slightly.

Tidal Power

According to Technology Review (online - 29 June 08) a 1.8 MW Irish tidal power project will cost $7-8 per W and provide the 1.2 kW needed per home.