The wind energy challenge
Question:
There’s been a lot of talk about how wind energy is now a conventional energy source, and it won’t be long before significant parts of our electricity consumption is provided for by wind. My skepticism towards alternative energy sources is well-known, so I’ll refrain from commenting directly. I would just like to point out a few facts. A power utility has the responibility for two distinctly different services to its clients: The supply of ENERGY, and the supply of POWER. In other words, not only must your local utility provide you with ‘x’ kilowatt-hours per year, but also precisely when you need it. Consequently, I propose the following simple analysis to compare conventional plants to wind: On an ENERGY perspective: All over the world, the typical power factor (Average power/installed capacity) of fossil fueled and hydroelectric plants is around 60%. Nuclear plants often reach 80%. This means that a good 1000 MW nuclear plant will produce about 33% more energy per year than a 1000 MW coal plant. However, windfarms have their factor at 20% in optimally chosen areas. In Denmark, for example, where the winds are particularily exceptional, this factor is only 22% on average. (In 1996, it was only 17%, due to unusually low winds) This means that 300 MW of wind turbines are required to produce as much energy as a single 100 MW coal plant. To replace a single 1400 MW nuclear plant, such as there are numerous in France, one would need about 5600 MW of wind turbines, which is over three times the US’s installed capacity. In a POWER perspective: All conventional power plants (fossil, nucelar, hydro) and biomass can provide 100% of their installed capacity at any given time, assuming sufficient fuel is readily available, and no upgrades/repairs are being done. The grid operator can simply order more fuel feed to increase power. As such, the grid’s ‘installed capacity’ is the total of all the installed capacities of its power plants. However, due to the wind’s intermittent nature, none of the windfarm’s capacity can be accounted for in the grid. Since we cannot be guaranteed that the wind will be blowing when we want it to, we don’t know how much power will be coming from wind. That’s why windfarms cannot replace any powerplants whatsoever. If properly used, they may replace a certain amount of fossil fuel burned, wich is good for the environment, but bad for the pocketbook. Some windfarms may be in exceptionally good sites, where, at most, 10% of its installed capacity can be guaranteed. To avoid making this post too long, I will post an example of a power/energy scenario in a second post. — Philip Coletsos
Response:
I look forward to the remainder of your message. As a wind power supporter and member of the industry I have to agree with much you say. Wind power does not provide "firm" power – it cannot be scheduled in the conventional sense. However, suspecting where your analysis is heading, I would like to jump in and make some salient points and point out a few minor errors in your "facts". Minor Points: You said that "windfarms have their "power factor" (I think you mean capacity factor) at 20% in optimally chosen areas". The concept of optimal is probably national. Here in the UK all wind farms have capacity factors exceeding 20% and around 35-40% is the norm. In Scotland we are experiencing projects with 40-50% capacity factor and are developing at least two projects with capacity factors in excess of 50%. Secondly in the UK we certainly do not expect the larger conventional plant to reach the capacity factors you cite. General Issues: You try to lead the reader down a route which states that wind power cannot replace a single power plant whatsoever. In a mature electricity supply system you are quite wrong.. I will explain. In the UK for example, it has been agreed by both the wind industry, the utilities and the government, that 20% of our total electricity demand could be replaced by a non-firm power source such as wind – that is technically possible without modification to the operation of the electricity network. (I note that nuclear provides around 20% of UK total electricity so this is an interesting measure of "worth") When wind power penetration is a low percentage of the total demand (as now) it is unlikely to impact upon the total number of power plants, but it will substitute for fuel use. As the penetration ratio increases, however, some plants on the system will become marginalised. Remember that there is always and intentionally overcapacity and that the role of each plant is not simple – some are used for base load, some for peak provision etc. When the wind penetration is high it is possible for it to totally displace some of the plant that is used for marginal operations (typically coal plant is this is usually the highest cost marginal fuel). To understand this from another perspective, remember that demand is constantly fluctuating. The introduction of wind is effectively, to the network, a subtration from that demand profile. At high penetration the effect is a susbtantial reduction in the overall though the peaks may for short periods remain the same. A further point which is quite important is timing. Studies of the half hourly grid demand in the UK has shown that they correlate well with wind speed. That is wind tends to generate when the demand is high (i.e. wind induced heating loss in buildings) and also when the spot price for electricity is high. OK so that’s enough for one message. A few other issues you might like to ponder are: - wind power is now in the UK and Eire, significantly cheaper than the average price of fuel in the system - ever thought why utilities offer cheap rate off-peak electricity – because those high capacity factor power stations are hard to control and its better to give the power away cheap than to change output (nuclear) – this reduces the value of the "capacity factor". - people do care about the environment and overwhelmingly support wind power – strangely they don’t give the same support to nuclear or fuels like orimulsion! Robert Forrest Energy Unlimited
Response:
As another wind power supporter and a another member of the industry, I thank you for your comments. I learned from them and I agree that wind can provide 20% (or more) of the total kilowatt-hours, and that it can displace other sources of electricity. I wonder if you agree that nuclear, like wind, is cleaner than fossil. John Hughes – Hide quoted text — Show quoted text – > I look forward to the remainder of your message. > As a wind power supporter and member of the industry I have to agree with much > you say. Wind power does not provide "firm" power – it cannot be scheduled in > the conventional sense. > However, suspecting where your analysis is heading, I would like to jump in and > make some salient points and point out a few minor errors in your "facts". > Minor Points: > You said that "windfarms have their "power factor" (I think you mean capacity > factor) at 20% in optimally chosen areas". The concept of optimal is probably > national. Here in the UK all wind farms have capacity factors exceeding 20% and > around 35-40% is the norm. In Scotland we are experiencing projects with 40-50% > capacity factor and are developing at least two projects with capacity factors > in excess of 50%. > Secondly in the UK we certainly do not expect the larger conventional plant to > reach the capacity factors you cite. > General Issues: > You try to lead the reader down a route which states that wind power cannot > replace a single power plant whatsoever. In a mature electricity supply system > you are quite wrong.. > I will explain. > In the UK for example, it has been agreed by both the wind industry, the > utilities and the government, that 20% of our total electricity demand could be > replaced by a non-firm power source such as wind – that is technically possible > without modification to the operation of the electricity network. > (I note that nuclear provides around 20% of UK total electricity so this is an > interesting measure of "worth") > When wind power penetration is a low percentage of the total demand (as now) it > is unlikely to impact upon the total number of power plants, but it will > substitute for fuel use. As the penetration ratio increases, however, some > plants on the system will become marginalised. Remember that there is always > and intentionally overcapacity and that the role of each plant is not simple – > some are used for base load, some for peak provision etc. When the wind > penetration is high it is possible for it to totally displace some of the plant > that is used for marginal operations (typically coal plant is this is usually > the highest cost marginal fuel). > To understand this from another perspective, remember that demand is constantly > fluctuating. The introduction of wind is effectively, to the network, a > subtration from that demand profile. At high penetration the effect is a > susbtantial reduction in the overall though the peaks may for short periods > remain the same. > A further point which is quite important is timing. Studies of the half hourly > grid demand in the UK has shown that they correlate well with wind speed. That > is wind tends to generate when the demand is high (i.e. wind induced heating > loss in buildings) and also when the spot price for electricity is high. > OK so that’s enough for one message. A few other issues you might like to > ponder are: > - wind power is now in the UK and Eire, significantly cheaper than the average > price of fuel in the system > - ever thought why utilities offer cheap rate off-peak electricity – because > those high capacity factor power stations are hard to control and its better to > give the power away cheap than to change output (nuclear) – this reduces the > value of the "capacity factor". > - people do care about the environment and overwhelmingly support wind power – > strangely they don’t give the same support to nuclear or fuels like orimulsion! > Robert Forrest > Energy Unlimited
Response:
: Minor Points: : You said that "windfarms have their "power factor" (I think you mean capacity : factor) at 20% in optimally chosen areas". The concept of optimal is probably : national. Here in the UK all wind farms have capacity factors exceeding 20% and : around 35-40% is the norm. In Scotland we are experiencing projects with 40-50% : capacity factor and are developing at least two projects with capacity factors : in excess of 50%. To increase the capacity factor, all you need to do is reduce the size of the generator, while keeping the blades and tower height the same. Costs go down somewhat, capacity factor goes up, overall production goes down slightly. One must calculate if, for the specific site, lost production is offset by reduced costs using a smaller generator. i.e. A 1000kW generator having a 20% capacity factor will produce more than a 500kW generator at 35% on the same windmill. The difference in production is only 220 kWh per year (12% less than the 1000kW’s production). Does this loss in production justify savings on the smaller generator? I guess it depends greatly on how much you’re selling the energy and just how much your building costs are. : Secondly in the UK we certainly do not expect the larger conventional plant to : reach the capacity factors you cite. Well, Hydro-Quebec’s only nuclear power plant curently operates at 80%, and in the past, Ontario Hydro’s nuclear plants operated frequently at over 85%. Hydroelectric dams help immensely, as they are an extremely efficient storage method. : General Issues: : You try to lead the reader down a route which states that wind power cannot : replace a single power plant whatsoever. In a mature electricity supply system : you are quite wrong.. I see what you mean, but if you plan to run a responsible power grid, you need a margin between your total installed capacity and your projected peak production for the year. This margin is ususally about 20%. If wind penetration is small (let’s say 1%), and you replace, a small gas plant, the difference is barely noticeable. Chances are, your grid will be as reliable as ever. In fact, however, the margin has been reduced to 19%. Still comfortable, but reduced nonetheless. If wind penetration is strong, one MAY choose to consider a part of the installed capacity as ‘firm’, meaning that statistically, at least ‘x’percent of the windfarms will be operational at all times, or at least, at certain times of day. — Philip Coletsos
Response:
I think we are all missing the point here. It’s nice that a country or a power company can have the foresight to produce X% of their power from wind generators. However, I have seen, actively participated in, helped construct individual farm or residential (in a rural setting) wind systems that provided 100% of the power consumed (except for wood heat and/or cooking) and have seen systems integrated with methane gas production to provide all power for a farm. It’s not what a company or state can do but what we as individuals can do. If we take care of our own needs then the "system" can go do it’s own thing, whatever that is. Dave
Response:
John Hughes wrote…. >I wonder if you agree that nuclear, like wind, is cleaner than fossil.
Ho hum, the old nuclear biscuit. To answer whether nuclear is cleaner than fossil fuels would require a definition or agreement of what cleaner means. Disasters aside, at the point of operation, nuclear certainly generates less atmoshperic pollutants. However, in order to carry out that generation the rest of the fuel cycle (raw material extraction, processing, re-processing, storage and disposal) are all energy intensive activities and aside from their use of fossil fuels (e.g. for transport), they eventually result in nuclear waste. Given that some of the products of the nuclear fuel cycle are among the most toxic known to mankind, then I find it hard to call nuclear "clean". There is one area of this that I would like to understand better. I have seen references to work carried out (by greenpeace I think) on the whole life cycle energy balance of nuclear which I recall stated that nuclear power was in fact a net energy consumer. As with other commodities, though, it may still generate net income for the operator. This is something we are trying to get funding to evaluate – my company has experience of carrying out life-cycle environmental assessments of energy projects, but haven’t done nuclear yet. Dependent upon the above analysis, it is therefore hard to tell whether nuclear emits less CO2 etc than fossil fuels (and we would like to compare nuclear against coal, oil and gas as well as against the renewables). At a policy level, the question has to be, do we replace fossil fuel with more nuclear? This is tough as it raises questions such as – employment (higher for fossil), long term waste storage, global climate change (which technology is better?), public acceptability, economics (in the UK at present nuclear seems to be more expensive than coal, gas, hydro and wind power) and security of supply / diversity of supply issues. Sounds like I’m sitting on the fence there – what is my preference for an energy future? It would be to start with maximising the use of clean fossils in the near term, whilst promoting significant uptake of a range of renewables to give diversity and security (and high capacity factors), along with legislation and funding for energy efficiency. In my portfolio I have no place for nuclear as I view the risk-reward profile as highly negative. I would be interested in others views on this. Rob Forrest
Response:
Dave Paxton wrote… >I think we are all missing the point here.
and… >If we take care of our >own needs then the "system" can go do it’s own thing, whatever that is.
Dave, I agree to a certain extent. Specifically, I agree that if everyone took more responsibility for their energy use then it would be possible to both substantially reduce the demand for energy (and hence reduce the pollution associated with energy production) and also to generate from more environmentally benign sources. We too design and install autonomous power systems to give total isolation from the grid. However, this is not a solution for everyone. There are reasons why not… economics – the costs tend to be high per kWh compared to grid power & the capital costs are very high – many people cannot raise the capital regardless of how financially attractive it may appear on paper technology – not all of the people could access the renewable resources to go independent – in cities and urban areas and indeed many rural areas are not suitable social issues – many people don’t want to get involved at that level in their energy supply But this also misses many issues. Movement of the whole network onto more acceptable sources would have a lower financial cost and lower environmental impact than take up by individuals. It would be more adaptable, capable of dealing with changes in demand, updates in technology etc etc. I think there is always a strong and important place for small renewable systems, but it isn’t the answer to our current energy problems. I also don’t concur with the philosopy that I’m OK and don’t care about the system. You can’t step outside the system – where did the energy come from to make your remote renewables plant, what energy was used to transport it to site etc etc – we have to care about the system as well as our own actions. Rob Forrest Energy Unlimited Scotland
Response:
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