In his July 3 column, George Monbiot reminds us of how much worse the threat of global warming may be than the consensus IPCC position. But he also reminds us that there are reasons for optimism too. He cites three studies that point to the fact that there is every reason to believe Europe and the UK can supply between 80 percent and 100 percent of electricity needs completely sun, wind, water, wave, tide, and minor amounts of biomass and geothermal energy, V2G Vanadium flow batteries, and pumped storage.
Given that electricity can drive just about all energetic processes of our civilization -- domestic, commercial, industrial, and transport, that means that we have economically reasonable substitutes for just about all carbon use now.
According to Monbiot:
Last year, the German government published a study of the effects of linking the electricity networks of all the countries in Europe and connecting them to North Africa and Iceland with high voltage direct current cables. This would open up a much greater variety of renewable power sources. Every country in the network would then be able to rely on stable and predictable supplies from elsewhere: hydroelectricity in Scandanavia and the Alps, geothermal energy in Iceland and vast solar thermal farms in the Sahara. By spreading the demand across a much wider network, it suggests that 80% of Europe's electricity could be produced from renewable power without any greater risk of blackouts or flickers.
At about the same time, Mark Barrett at University College London published a preliminary study looking mainly at ways of altering the pattern of demand for electricity to match the variable supply from wind and waves and tidal power. At about twice the current price, he found that we might be able to produce as much as 95% of our electricity from renewable sources without causing interruptions in the power supply.
Now a new study by the Center for Alternative Technology takes this even further. It is due to be published next week, but I have been allowed a preview. It is remarkable in two respects: it suggests that by 2027 we could produce 100% of our electricity without the use of fossil fuels or nuclear power, and that we could do so while almost tripling its supply: our heating systems (using electricity to drive heat pumps) and our transport systems could be mostly powered by it. It relies on a great expansion of electricity storage: building new hydroelectric reservoirs into which water can be pumped when electricity is abundant, constructing giant vanadium flow batteries and linking electric cars up to the grid when they are parked, using their batteries to meet fluctuations in demand. It contains some optimistic technical assumptions, but also a very pessimistic one: that the UK relies entirely on its own energy supplies. If the German proposal were to be combined with these ideas, we could begin to see how we might reliably move towards a world without fossil fuels.
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Comments
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sunflower Posted 3:17 am
09 Jul 2007
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Kristina & Jason Makansi Posted 4:11 am
09 Jul 2007
The potential for confronting our challenges exists...the question is whether the political and personal will is there or not as well.
Pearl Street/Jason and Kristina Makansi
Learn more and order Lights Out at http://www.jasonmakansi.com/lightsout_endorsements.html
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Gar Lipow Posted 5:30 am
09 Jul 2007
I think it depends more than you think:
First for new buildings I don't think there is a question you are right. There is no reason a new building should use electricity for anything but backup when it comes to climate control, hot water and other low temperature grading uses. And low temp thermal storage means even that should come from off peak electricity.
For existing buildings it is not so clear. If you are using a ground source heat pump then you are getting 2-3 units of heat or cooling for each unit of electricity input; you are making up for your thermodynamic losses. In general, in an existing building with poor solar orientation, you may be able run ground source heat pumps on a renewable grid less expensively than retrofitting district heating. For that matter district heating may find that ground source heat pumps are more economical that solar panels.
As to biomass for energy-you can get better value from the biomass by using it as feedstock for chemicals, and for other uses where we really can't avoid the use of hydrocarbons. Absent breakthroughs in cultivation of algae, Kelp and other sea plants we can't produce all that much fuel biomass sustainable--so we should not use it where there are other low carbon alternatives.
Note to lights out. Everything you mention is actually included in the studies except CAES--reduced use, a better grid and so.
The problem with our current generation of compressed air is that it is not adiabiatic. To recover power from the compressed air you have to heat it before feeding it into a turbine. So you end up recovering a fairly low fraction of the power you put in (40%-50%), and you still have get about half the power in any turbine you use the compressed air in from natural gas. The EU is fundng research on storing heat generated during compression. They hope eventually to be able to recover 60%-75% of the power that is input, without any need to burn fuel during recovery. But there is not even a prototype at present.
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sunflower Posted 6:59 am
09 Jul 2007
Overall, entropy doesn't decrease with heat pumps.
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Gar Lipow Posted 8:15 am
09 Jul 2007
For example take two examples:
You use gas derived from biomass to heat a home. You use the most efficient heat available; so you 95% percent of the energy in that gas derived from biomass is turned into usefulh heat:
You burn gas from biomass in a combined cycle turn, converting 60% of it into electricity. You lose ten percent of that in transmission-- so electricity reaching the home is about half the energy in that gas. A ground source based heat pump pumps 2 to 2.5 units of heat into the house for every unit of electricity consumed.
So you end getting more heat for your home out each unit biogas with the ground source electric heat pump than you would with a super efficient gas heater. Of course the electric heat pump costs you more than the gas heater; and presumably we try to power it by wind (and other renewable)electricity rather than biogas as much as possible. There is a lot more potential for the former than the latter. To the extent we do use fossil fuel for electricity we will try to locate generation where the waste heat can be tapped for low temp uses -- reducing the number of heat pumps we have to use.
None of this means we don't do efficiency first. But we are talking about how to generate energy once we have saved all we can, and put all the low temperature solar thermal in place it makes sense to.
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Kristina & Jason Makansi Posted 3:20 am
12 Jul 2007
You say: "The problem with our current generation of compressed air is that it is not adiabiatic. To recover power from the compressed air you have to heat it before feeding it into a turbine. So you end up recovering a fairly low fraction of the power you put in (40%-50%), and you still have get about half the power in any turbine you use the compressed air in from natural gas."
This comment is true. However, in current systems the stored air is heated using an open cycle gas turbine (GT) reducing the heat rate (fuel consumption-Btu/kW/hr) from 9215 Btu/kW/hr to 3900 Btu/kW/hr for the total plant. (90MW of GT will have a plant rating of 220+ MW). The GT hot exhaust (1000 degrees F) is recovered to preheat the stored air before adiabatic expansion. The expander exhaust has no combustion products and the stored wind or renewable energy remains "green". Biomass pelletized fuel can also be used in air preheaters as well, making the system CO2 neutral.
As current CAES systems are utilized to extend the wind energy capability and provide dispatchable capacity, more development can be focused on TES (thermal energy storage) and the ideal storage media. There is no lack of investigation here--some very smart people have been working on this idea since the 80's. It is time to really take another look at development of this technology.
"The EU is fundng research on storing heat generated during compression. They hope eventually to be able to recover 60%-75% of the power that is input, without any need to burn fuel during recovery. But there is not even a prototype at present."
Quoting from the EU report on the research cited above, the project "addresses the development of a technology enabling cost-effective and efficient medium to long-term storage of electrical energy through the medium of compressed air. The project incorporates a consortium broad and strong enough to simultaneously address all of the issues to be solved. It studies the development of heat storage devices enabling effective adiabatic CAES technology; adiabatic or quasi-adiabatic compressors able to deliver compressed air at sufficiently high temperatures (400 °C / 650 °C) and pressures (8 - 16 MPa); and expansion turbines enabling fast start-up, high power-ramps, and high efficiency over a broad range of inlet pressures. It couples these component developments with generation of basic data allowing for accurate process simulations and traceable performance tests for turbo machinery and heat storage devices; a reliable economic model describing all the benefits of electrical-energy storage; and a study of geological and geographical constraints.
The approach is to evaluate very different technical solutions in a first phase, to concentrate on 2 - 3 technically and economically viable solutions for different market scenarios in a second phase and to establish a conceptual design for the economically most attractive product in the third phase of the project. Emphasis early in the project is given to the critical issues of market and economic analysis and to the critical technical issue of the heat storage device."
The result of this study defined the viability of current sized air compressors and IP steam turbine designs that will expand the air adiabatically. The part that is lacking is the Thermal Energy Storage (TES) from compression. When the cost of TES is controlled and suitable media can be developed, then the system can be quickly deployed (note that TES systems have been researched and utilized with Solar-Towers--though the cost is still high.)
The current thinking within the research community is to utilize the 30 MW/150 MW/300 MW systems using NG to preheat the air before expansion.
However, adiabatic CAES has been demonstrated http://www.eniswindgen.com. While this is small scale, units of 500kW and increments thereof are available. The resultant cold air from expansion can be used for TES (one kW electrical power generation will provide one kW of thermal energy) other uses are cold storage warehouses, HVAC and desalination of brackish or salt water. The stored energy (CAES) in pressure vessels or large diameter pipe is harvested from wind during night time or excess spilled wind. The efficiency is less important than the ability to deliver capacity on demand--as is the reduction of CO2 emissions.
There are many variations of CAES that can be utilized today, and improved with TES. As the renewable industry realizes the "value-add" component of capacity and dispatch guarantees during high demand, increased acceptance and demand for wind energy will help offset the higher initial costs for storage systems.
Pearl Street/Jason and Kristina Makansi
Learn more and order Lights Out at http://www.jasonmakansi.com/lightsout_endorsements.html
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Gar Lipow Posted 4:15 am
12 Jul 2007
Wow! Good information! Thanks.
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amazingdrx Posted 5:03 am
12 Jul 2007
Conservation and storage have run together. Using the earth as a heat sink can vastly reduce energy use for heating/cooling, maybe even by 90%.
And using homes and buildings, freezers and refrigeraters, and hot water heaters to store energy and also allowing the grid to shut down these loads on demand, can supply all the smoothing of variable power available from renewable sources that is needed.
Internet controllable switching of appliances and heating/cooling systems is needed to facilitate this trend. And internet over the power grid.
It is no longer necessary to cede the issue of energy grid reliability to the dark forces of fossil and nuclear corporatism.
http://amazngdrx.blogharbor.com/blog
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