Posted by Max Dunn
Fri, 06 Nov 2009 02:12:50 GMT | 2 comments
What is better – to save water or to save electricity? This is a tradeoff that businesses and industry concerned about sustainability often need to make, and it is not an easy one.
However, an article in the November 6th, 2009 edition of The Economist called Current thinking: Cheaper desalination provides this tidbit: “Even the best reverse-osmosis plants require 3.7 kWh of energy to produce 1,000 litres of drinking water.”
Converting to gallons, this means that 70 gallons of water can be produced from salt water with 1 kWh of electricity. So there we have it – a way to compare water savings to electricity savings.
Posted in Sustainable Energy
Posted by Max Dunn
Fri, 18 Sep 2009 02:27:41 GMT | no comments
Here is a study that looked at Energy Return on Invested (EROI) of windmills and found they returned over 20 times the energy use to make them, which is favorable with fossil fuels, nuclear and solar power.
Meta-analysis of net energy return for wind power systems
Posted in Sustainable Energy
Posted by Max Dunn
Thu, 10 Sep 2009 21:34:37 GMT | 1 comment
Some people claim that more energy goes into making a solar photovoltaic (PV) panel than it will ever produce. While years ago that may have been the case, it certainly isn’t true any longer.
The US Department of Energy looked at several studies and concluded that multi-crystalline PV has an energy payback of less than 4 years and this will likely go down to below 2 years soon. Thin-film technologies have an even shorter payback period. With an estimated 30-year life, solar PV is actually a very good energy investment!
Posted in Sustainable Energy
Posted by Max Dunn
Tue, 28 Jul 2009 14:32:11 GMT | no comments
When looking at the economics of building solar panels, one important factor is how much the factory costs.
By comparison, the fuel for a nuclear power plant is very inexpensive and the main reason why nuclear power is so expensive is that the nuclear plants cost so much to build. Is this also true for solar panels? Do solar panel factories costs so much that even if the marginal cost of producing a solar panel comes down, will the cost of the factory still keep the prices high?
If the recent announcement of a thin-film solar panel factory is any indication, then solar panel plant costs are very low.
This factory will cost about $150 million dollars and produce 100 MW of solar panels per year. Over 10 years, this will add only $0.15 per watt to the cost of the panel. Considering that we only need to get solar power down to about $2.00 per watt to be competitive to coal, the cost of the factory is not a problem.
So it appears that the cost of solar panel factories will not be the limiting factor in bringing down the cost of solar power.
Posted in Sustainable Energy
Posted by Max Dunn
Sat, 25 Jul 2009 15:08:16 GMT | no comments
A friend of mine recently got a 400cc Suzuki Burgman scooter and loves it. He gets 53 MPG which is pretty good, but realized that it was about the same as a Prius that gets 48 MPG. “Why is this?”, he asked. The Prius weighs about 3000 lbs while the scooter is only 400 lbs.
Let’s look into this.
Regenerative Breaking
Even though the scooter is a lot lighter, the Prius captures about 50% of the energy when breaking and uses it to accelerate. So this brings the effective weight of the Prius down to 1500 lbs.
Wind Resistance
Even though the scooter has a frontal area 4 times smaller than a Prius, a scooter is not very smooth going through the air. It has a coefficient of drag (Cd) of about 0.9 versus about 0.26 for the Prius. Adding this up, the total drag coefficient (Cd x A) for the Prius is 6.24 and the scooter is 5.4. This means that the scooter takes almost as much energy to overcome wind resistance as the Prius!
Motor Efficiency
Small engines are not very efficient, while Prius engines are very efficient.
Conclusion
Add them up: the extra weight is not as significant because of regenerative breaking, the wind resistance is about the same and the motor is much less efficient. Given all this, it is not surprising that the scooter and the Prius get about the same gas mileage!
Posted in Sustainable Energy
Posted by Max Dunn
Tue, 12 May 2009 16:13:05 GMT | no comments
- Michael Reilly, Discovery News, May 11, 2009 – Forget peak oil, a series of new estimates of the world’s coal supply suggests reserves may be vastly overestimated, and if the planet isn’t running on a majority of alternative energies within the next few decades, we could be facing an unprecedented global energy crisis.
On the flip side, a dwindling supply of coal could also throw the breaks on global warming, some argue.
Common knowledge about coal is that major producing nations like China, the United States and Australia, have enough to last hundreds of years, far beyond the reach of oil, which may already be in its twilight years. But worldwide coal production could plateau as early as 2025, according to one new estimate, and a growing group of scientists are concerned that fossil fuel supplies may begin dwindling by mid-century.
Last year, David Rutledge of the California Institute of Technology analyzed the coal production patterns of five regions around the world – eastern Pennsylvania, France, Germany’s Ruhr Valley, the United Kingdom and Japan – each of which was producing at less than a tenth of its peak levels.
He found that each of the depleted regions followed a rough bell curve of production; initial production was followed by a steep ramp-up, a plateau near peak levels, and then a consistent decline.
When he applied the same formula to coal data from around the world, the results were startling: the United Nations Intergovernmental Panel on Climate Change’s maximum estimate for extractable coal is about 3,400 billion tons. Rutledge’s calculations suggest just 666 billion tons.
Read more...
Posted in Sustainable Energy
Posted by Max Dunn
Fri, 27 Mar 2009 14:47:19 GMT | no comments
Negawatts is term coined by Amory Lovins to describe “negative watts” or conservation. It makes sense – instead of constantly building power plants to add more megawatts to the grid, why not let people bid on saving power through negawatts? That’s what New England’s independent system operator started doing last year.
In its Forward Capacity Market, the ISO projects how much power the region will need three years ahead and then runs a descending-clock auction for the right to provide it. The ISO doesn’t care whether it gets its power from increased production of megawatts or from conservation through negawatts. Result: money saved in power plants and wires, more stable electricity bills, and a homegrown incubator for getting bright green ideas off the drawing board.
(Source: Wired Magazine Trade – Electricity Like Pork Bellies)
Posted in Sustainable Energy
Posted by Max Dunn
Thu, 19 Mar 2009 20:31:25 GMT | no comments
A recent study by Mark Jacobson at Stanford ranks clean energy options and found that wind was by far the most promising. The best to worst electric power sources Jacobson found were:
- Wind power
- Concentrated solar power
- Geothermal power
- Tidal power
- Solar photovoltaic
- Wave power
- Hydroelectric power
- Nuclear/coal with carbon capture
Jacobson also comes down hard on biofuels, “Biofuels are the most damaging choice we could make in our efforts to move away from using fossil fuels.” He added, “Ethanol-based biofuels will actually cause more harm to human health, wildlife, water supply and land use than current fossil fuels.”
(Reference: Wind, water and sun beat other energy alternatives, study finds)
Posted in Sustainable Energy
Posted by Max Dunn
Thu, 19 Mar 2009 04:38:23 GMT | no comments
What does it cost to build a new electric power plant? Here is a graph that shows this:
However, you do need to adjust this for utililization, since nuclear operates about 90% of the time, while solar operates only about 20% of the time:
(Source: What does Sustainability Mean for Energy?)
Posted in Sustainable Energy
Posted by Max Dunn
Fri, 27 Feb 2009 04:03:36 GMT | no comments
I just went to an interesting talk about distributed solar and found out that prices of solar PV panels are dropping dramatically. Soon, PV will be about $4 per watt installed (in large installations) which works out to about $0.17 per kWh.
By comparison, coal-fired electricity sells for about $0.05 per kWh. This includes about $0.02 for the coal itself ($2.15 per MMBtu and 1 MMBTU produces about 100 kWh) and $0.03 for all other expenses.
Adding in a $30 per ton CO2 tax would add about $0.03 per kWh to this price, (coal produces about 2 lbs of CO2 per kWh) for a total of $0.08 per kWh.
So even with a CO2 tax, coal electricity will still be half the cost of PV.
Therefore, for coal electricity to cost about the same as PV electricity, a tax of 400% would need to be added to coal!
Posted in Global Warming, Sustainable Energy