The essential energy system -- fact and fable

Everyone can agree that the perfect electricity system is one which is both affordable and ecologically sustainable. Achieving that aim is the subject of serious worldwide debate, from the vaunted academic halls of the experts advising the United Nations on climate change to backroom government committees struggling with new market regulation. The aim of this article is to clear some of the fog surrounding renewables and strategy. In a world where energy consumptions is growing at 2.2% a year and renewable energy at just 2%, it is important to have a clear view.

Google Translate

Governments are seldom privy to objective advice which takes account of all the relevant issues. They are assailed on all sides by pundits, lobby groups, think tanks, soothsayers and visionaries, followed by layers of advisory committees who are supposed to sort spin from salient fact. Nowhere is this more true than with energy strategy. Injecting some objectivity is the aim of this article, though restraining wind from assuming a star role had us under duress

Typical statements of fiction heard at conferences and appearing in reports over past weeks are these: "large power stations are a very inefficient way of delivering electricity;" "hydrogen fuel can solve our energy problems;" "fuel cells are the future;" and "micropower will replace central generation and the grid will just be a backup." There is an appalling consequence to such sweeping solecisms: the fact that renewable energy is the key component for the perfect electricity system is still largely being treated as the stuff of fable.

The perfect electricity system is one which is both affordable and ecologically sustainable. Achieving that aim is the subject of serious worldwide debate, from the vaunted academic halls of the experts advising the United Nations on climate change to backroom government committees struggling with the details of new market regulation. Fogging that debate are a myriad of half truths and misplaced facts. Sometimes they stem from propaganda from the established energy industry. Just as often, however, they are the result of genuine misunderstandings from visionaries and policy advisors.

It is the job of governments to sort fact from fable and to provide clear-cut strategies to solve the world's energy and environment problems. With those strategies in hand, legislatures can structure markets that result in the perfect energy system. Any strategy worth the writing must be founded on solid facts about what the available technologies can deliver today, their potential for delivering tomorrow, and which technologies are so unlikely ever to deliver that it is not yet worth including them in the process. Those facts are not so much missing from the current debate as lost in a fog of fiction. Clearing some of the fog is the aim of this article.

Strategy priorities -- step one

Not all the renewable energy technologies have moved from the realm of science fiction into the commercial world. Some may never do so, and only then if demand should exceed the economically exploitable resources of the more advanced renewables. Wind has proved that it can deliver sufficient clean electricity, both on a sensible timescale and at an acceptable cost. For policy strategists, identifying which technologies can follow wind's lead, which might be able to do so, and which do not deserve any attention at all (table page 60) is a key first step for instructing legislators. At the same time they must assess which technologies can best deliver each form of energy -- production of heat, production of electricity, or production of both in combined heat and power plant (table page 57). The assessment is straightforward, but it must be part of a strategy from the outset if the costs of a clean energy system are not to be pushed up unnecessarily.

Identifying which technologies can best deliver the needs of clean energy systems reveals that fuel cells and micro turbines do not deliver electricity without contributing to global warming. Far from it. Their inclusion in the renewable energy debate is by default -- and is a serious contributor to the fog-factor. The confusion has come about because the debates on "renewable energy" and whether centralised power systems can cope with "distributed generation" are historically intertwined, due to the small scale origins of renewables. Yet while fuel cells and micro turbines are clearly part of the distributed generation debate, they are not renewable energies; and while renewable energy plant can be distributed, that is not where the main future lies for all of the technologies.

Strategy step two

Thus a second key step for strategists is to distance themselves from the automatic presumption that "renewable energy" and "distributed generation" are two sides of the same coin. The distinction will be vital for wind and several of the other renewables. Modern day wind power is often at its most viable in larger plant, onshore where possible, such as in Spain, North Africa, China and the United States, and otherwise offshore. The world's most advanced biomass plant is a 500 MW CHP unit near Copenhagen, Denmark, going on-line this year. These developments are not distributed generation. Indeed, large renewable energy plant are just as reliant on a transmission system geared to centralised power generation -- and customers a long way away -- as are the conventional thermal technologies.

That is not to say that the same power system cannot also be adapted so that micro-power sources, renewable or not, can feed increasing quantities of local generation into electricity networks. There may well be valid reasons for to encourage this to happen; improvements in electronic controls and information technology make such power system improvements possible. They also become viable when tackled as part of an evolutionary process rather than a revolutionary one.

Fuel cell fiction

Fuel cells are not a renewable energy source. They produce electricity from hydrogen and oxygen, but that hydrogen must either be generated by electrolysis, or by chemical reaction from natural gas. Either way, greenhouse gas emissions are produced. Large combined cycle gas turbines, far dirtier than wind power, generate lower emissions than fuel cells.

For transport, the attraction of fuel cells is that they produce no harmful emissions from the vehicle. But the vision held by America's Electric Power Research Institute (EPRI) of millions of these vehicles feeding into home power systems whenever they are parked is a frightening one for the environment. Fuel cells only generate zero emissions if the electricity used to produce the hydrogen comes only from renewable energy and nuclear power. Although that is the eventual goal of the fuel cell enthusiasts, it is a long way off yet. It is also up to strategists to decide if building renewables plant to produce electricity to make hydrogen so that fuel cells can generate electricity is a rational approach to sustainable and affordable energy -- compared with the evolutionary route of adapting today's systems to a major role for the established renewables.

Microturbine myths

Microturbines -- gas powered units with rated capacities of around 10-100 kW suitable for installation in homes and buildings -- have even less claim as a renewable than fuel cells. The sales forecast for this year of 3500-5300 units by energy market intelligence company Primen will provide net electrical capacity of 200-300 MW; much of this will be for off-grid applications if last year's pattern is repeated.

As a distributed generation technology, and particularly off-grid, microturbines would appear to have a future, despite their emissions. But the belief that they can eventually displace conventional power stations, strongly promoted in some circles, is hard to justify on technical and economic grounds, let alone those of the environment. The efficiencies of micro gas turbines are around 30 percentage points lower than those of the largest units. That pushes up emissions, even allowing for losses in transmission and distribution. Even the most enthusiastic champions of small gas turbines do not expect their efficiency to climb much higher than 40%. That is nearly 20% less than achieved by large gas turbines today and their champions are aiming for 70%. With transmission and distribution losses in the developed world around 10% at most, modern combined-cycle gas turbines feeding into "conventional" electricity networks will deliver power to consumers with an overall efficiency around 50%. Since the efficiency of small-scale micro turbines and reciprocating engines is much lower, any wholesale replacement of large power stations by numerous smaller units will increase, rather than reduce, greenhouse gas emissions. Moreover, the claims that large plant are inefficient begs the question: how to do it better?

Clean coal & cheap gas?

Fact: thermal sources of electricity will continue to supply most of the world's needs for many years, even if renewable energy were to boom beyond what appears feasible in the most optimistic projections today. On current trajectories, renewables' contribution to electricity generation will increase marginally from 20.2% to 20.6% by 2020, according to the US Department of Energy. Although given the right policies (ratification of the Kyoto treaty) that figure could be much improved, fossil-fuel thermal will still dominate. It will not necessarily always remain cheaper than renewables, however.

"Gas is the fuel of choice" is a phrase frequently used and, until recently, gas was the cheapest electricity-generating option in many places. Steep price rises have eroded that attraction and there may be a growing realisation that the growth of demand may put resources under strain. What is more, in the context of sustainable development it makes little sense to burn a clean and flexible fuel in a power station -- with a maximum efficiency around 55% -- when, even in a domestic boiler, efficiencies at least 20 percentage points higher can be achieved. That argument underpinned a ban on the use of gas for electricity generation by the European Union, which was rescinded about ten years ago. If the current price levels inhibit further growth of gas-fired generation (as seems likely), this may be no bad thing as poor efficiency means more greenhouse gas emissions.

Coal is the dirtiest of the electricity generating options, but the most abundant. In many regions, it is the cheapest option and there is a school of thought that suggests it will remain so, even if it pays the cost of environmental compliance. That cost is low at the moment -- around $10/tonne of carbon dioxide. The fortunes of coal are therefore looking brighter, especially as large sums of money are being invested in "clean coal" research. The technology seems likely to become established within the next ten years -- if the pundits are to be believed. In terms of carbon dioxide emissions, clean coal achieves reductions around 15%, but the emissions are still significantly higher than those from gas. The future costs of environmental compliance are very uncertain.

Sexy sunshine

Wind power has never been able to attract the levels of public investment in research and development enjoyed by the solar technologies. Even so, it is wind that is selling power at commercial rates, not solar. Meantime, activity in solar thermal-electric technology, which uses mirrors to provide a source of heat to drive steam turbines for electricity generation, has declined in recent years.

Strategists must face the fact that though the solar resource is undoubtedly huge, capturing it at reasonable cost is proving difficult. Photovoltaic electricity costs are 10-20 times greater than those of wind. PV capacity is increasing at about the same rate as wind, but it is about a factor of ten behind. Extrapolating forward to 2020 suggests that wind capacity will have reached 1.8 million MW and PV around 180,000 MW. The output from PV devices is, however, about a half to one-third of the output from wind plant of the same capacity and so the electrical generation in 2020 would be about 3% of the output from wind.

In the developing world, the economics of electricity generation are often different from those in the developed world. The competing fuel -- if there is any -- is often imported diesel, generating high-cost electricity. Frequently there is no grid. In these circumstances, PV, with its absence of moving parts and low maintenance, is ideal. Even at its relatively high price it can be a cost effective option and the potential is truly enormous.

Thus logic dictates that strategists should concentrate their efforts on developing PV for these markets. The "solar roofs" initiatives of Germany and Japan will help bring down costs, but there is an argument that a more rational strategy would have been to devote the high levels of spending on introducing a technology to the developing world that prevents some of the need for new fossil-fuel generation. Even the PV industry, benefiting from considerable subsidies, is uneasy about the lack of a rational strategy. Trade association PV-UK has suggested a "road map," an idea similar to that developed by EPRI for the US electricity industry.

Wonderful water

Four renewable technologies: wave, tidal, tidal stream and hydro, harness energy from water. Hydro is possibly the most straightforward: the theoretical potential is very high, but it is generally accepted that further large scale exploitation in the developed world would involve unacceptable environmental disturbance due to the large areas of land that need to be flooded to make way for the larger schemes. A modest but useful additional contribution from small hydro schemes is expected in the short and medium-term -- and at modest cost. Market support should achieve this objective.

Tidal barrages, rather like large hydro schemes, have considerable potential but tend to be controversial on account of their environmental impact. As with hydro, the technology is proven, but interest tends to be focused on the larger schemes, such as the Severn barrage in England. As a result, the myth has arisen that tidal barrage power is expensive. But the generating costs would be modest -- around $0.10/kWh or less -- and there are many existing derelict dock-land sites and medium-scale estuaries worldwide which could be used to impound the water with low risk. The Australian government is looking at this option. The environmental impacts are minimal and could even be positive at some sites. Given that small tidal barrages successfully powered industrial complexes over 100 years ago, the lack of interest in demonstration programs to test the viability and economics of the concept at smaller scales is perplexing. A case for strategists, it would seem.

By contrast, the prospects for wave energy are distinctly uncertain and difficult to discern, yet Denmark, Japan, China, India and the EU have R&D programs and the UK has recently renewed its interest. On what basis remains unclear. The UK's own energy department states that after 30 years of worldwide research "none of the concepts has been demonstrated to be commercially viable, nor has their technical viability been demonstrated over any significant length of time." The resource might be huge, but compared with other renewables with an equally large resource, the problems are many. Neither is there any solution in sight to the two fundamental difficulties: the devices must convert the oscillatory motion of the waves into a constant rotary motion; and they must withstand the worst winter storms. If nothing else, a distinction has to be made in strategies between the simpler shore-line devices and more complicated offshore systems.

The energy in tidal streams and marine currents can be harnessed in a similar way to wind energy by immersion of small turbines, especially where tidal movements are amplified by the topography. But commercial exploitation requires stream velocities of around 2 m/s or more, which substantially reduces the feasible sites. But the advantages of the technology are straightforward: the energy availability is predictable; visual impact is low; and there are few environmental disturbances. The key aim here must be to encourage demonstration projects and targeted R&D beyond the limited number of small test models now operating, typically with devices rated around 10 kW.

Bountiful Biomass

The biggest dreams for renewable energy are inspired by biomass. Forestry by-products, straw and other agricultural wastes are widely used, both for electricity production, particularly in Scandinavia, and for heat, mainly in the developing world. As well as the environmental benefits for energy production, the dreams are also being driven by the spin-off attractions of extra subsidy-income from biomass crop production for hard pressed farmers. In the UK energy crops are expected to provide 3-16% of the 2010 target for renewables, while wind will provide 25-45%. The national renewables target is for one-tenth of the UK's electricity. The European Commission, however, has a far greater role for biomass than for wind, with biomass providing 8% for the whole of Europe, compared with only 3% for wind. The EU target for renewables electricity is 22% of consumption by 2010.

Whether the dreams are grounded in reality, particularly for electricity production in industrialised countries, is questionable. Development of higher temperature gasification techniques, which promise higher efficiency, is seen as the way forward, particularly connected with specially grown "energy crops." If all the unused agricultural land in the UK were used for this purpose, enough plant could be built to replace all the nuclear power stations. But there are still two problems. First, biomass will mainly only be competitive in Europe if linked to subsidies connected with agricultural land. Second, the advanced gasification techniques are sophisticated and there are difficulties in achieving high efficiency at small scale. Fiendish sophistication at small scale seldom makes engineering or economic sense. Development at large scale, however, is inhibited due to difficulties in bringing all the fuel to the power station; energy crops are much less dense than coal and so much greater volumes must be transported, with the additions to emissions of CO2 this entails.

The biomass industry is critical of governments for giving priority to the gasification route and neglecting "traditional" uses. The efficiency of traditional biomass electricity generating plant is not high, but if there is an available resource it makes sense to use it rather than let it rot and produce methane, a greenhouse gas. Particularly in the developing world there can be huge amounts of bio-waste from industry, such as the sugarcane industry, just rotting on the doorsteps of companies buying electricity from miles away or reliant on diesel generation.

Similar arguments apply to biogas produced by farm slurry, sewage gas and landfill sites in the developed world. Again, these should be exploited whenever possible, as they often are on-site at farms. Switzerland has gone a step further and is feeding biogas into the natural gas pipeline. The technology is proven and while still underused, its role in energy supply is undisputed, though limited by the availability of the resource.

And geothermal

Geothermal energy has been used for several thousand years and fable has long given way to fact. It originates from deep within the earth where high temperatures are found. The best geothermal resources are in the United States, the Philippines and Italy, which has the highest capacity of geothermal electric generation in Europe. Most European countries use geothermal sources for heat. Warm water reservoirs are the favourite method, but research is ongoing, particularly in America, into ways of improving drilling processes, using "hot dry rocks" as a heat source, and into alternative thermal cycles for harnessing the heat. But in Europe the resource is very limited. The EU's renewable energy guidelines (there is no renewables strategy) suggest electricity capacity may be doubled to 1000 MW -- and that heat capacity may increase from 1.3 to 5 GWth -- by 2010.

A word on wind

Wind power has its own fables. It would not be rational to base an electricity system entirely on wind power. To ensure a steady supply of power, a very large number of turbines would be needed over a very large area. Neither is it true that wind power on a large centralised electricity system needs dedicated back-up plant or storage. With large amounts of wind energy on an electricity system, some conventional thermal electricity generating plant needs to "cover" for wind energy -- but only a very small amount. Far more is needed to guard against failures of large steam turbines and transmission connections.

Another fable is that wind "cannot displace thermal plant." It can, as numerous hard-nosed utility studies have shown. Not everywhere, perhaps, but certainly in most of Europe and America. By contrast, solar energy is not available at times of peak demand in northern Europe so it cannot replace power plants there. It can in sunny climes, such as in Greece and California, when peak demand is for air conditioning during the day, the time when solar energy is most available.

Moving from fable, wind is heading for 145,000 MW by 2010, according to BTM Consult's just released World Market Update (page 52). Based on wind's long-term growth rate, however, the figure will be closer to 150,000 MW (enough to supply the UK's electricity needs) and just under 1.8 million MW by 2020 (enough to supply the whole of North America). These estimates are conservative, as they ignore the acceleration in growth during the last two to three years.

Prospects and projections

Getting the most out of any resource, whether it be a human resource or a technology resource, is a lifetime process. First there is a long period of learning, followed by demonstrations of lessons well-learned for those that emerge as winners from the formative stage. The next step is the trainee market with on-the-job support, which can be removed once the worker or technology is operating effectively and economically. Money must flow for performance related post-market training, or R&D, from this point, and does so naturally within the industry provided there is a competitive market to spur investment. In the energy strategy business, identifying which technologies lie where in this lifetime process is a vital first step. A pan-renewables strategy, part of an overall clean energy policy, must ensure that each technology is developed for the right market, with the right mix of R&D, and the right level of market support.

With the focus on electricity production, and setting aside nuclear and its problems, wind power and PV are the only energy sources with unlimited potential that ought to be in the market support bracket. PV support, though, should be directed at areas of the world where the sun shines when electricity is needed if the goals of an affordable and sustainable future are to be adhered to. Geothermal, small tidal barrage and hydro are in the market support category too, but with limited resources. With geographic adaptations, these technologies are receiving market support today, with the notable exception, however, of small-scale tidal barrage, which is mostly being ignored by governments for reasons unknown.

At the earlier demonstration stage are clean coal (included here because fossil-based thermal is part of the future and coal can and must be made cleaner), biomass gasification for more efficient electricity production, tidal barrage, tidal stream and PV, which though ready for market support for some applications has yet to demonstrate its commercial credentials. Tidal barrage is again getting a raw deal. Back in the pre-competitive R&D bracket are clean coal, biomass gasification, tidal stream and, yes, solar PV. Since tidal barrage is probably competitive it can leapfrog this stage, should it ever win favour again.

With the major renewables showing so much promise, funding wave technology seems to have no strategic purpose. Demonstration wave projects now operating might disprove the negative results of 30 years of testing so far. Even so, most energy projections for 2030 do not seem to include any significant contribution from wave energy, suggesting that governments have little faith that their backing of wave will bring results.

What of nuclear?

Nuclear remains a political problem of radioactive proportions. The industry is pushing nuclear's carbon-free credentials strongly, even saying the world can only meet its affordable and sustainable goal if nuclear is part of the strategy. The fog surrounding the fact that renewables can score the goal alone is allowing nuclear to get away with these claims, which governments are showing signs of believing. Nuclear's prospects have also improved during the past year or so as the developing world embraces the technology; costs are likely to come down with the construction of more plant. In addition a new type of reactor is planned by the South African utility, Eskom. Relatively small by nuclear standards, it enables some of the massive structures to be simplified or eliminated. But whether its claimed capital cost of $1000/kW can be achieved (about the same as wind) remains to be seen.

Governments are increasingly beginning to recognise that interlinked national strategies for rational development and use of renewables are vital. Moving from that realisation to strategy development is where they are stuck. They need to get a move on if climate catastrophes are to be avoided, or at least contained. World energy consumption is likely to grow at about 2.2% a year up to 2020, according to the US Department of Energy. Renewable energy, however, is growing at just 2% a year -- despite the impressive growth of wind power. The net result is that the renewable contribution to primary energy consumption is expected to fall from 9% to 8%. World carbon dioxide emissions will increase by about 50% by 2020, unless serious strategies are laid.

NOTE (accompanies graph on today's spending on energy/renewables R&D compared with tomorrow's generation costs): This chart is not an indication of current funding, but a wish list for the way it should be. The list starts with nuclear which has no need of help to the market (but is still getting it), followed by a group of five which have reached the market support stage. The pre-market group is headed by small tidal barrage, which is ready to demonstrate its credentials, but is not being allowed to, followed by a group still in concentrated R&D. Lastly, early solar thermal demonstrations have not proved the technology is affordable, while wave is so uncertain that giving it more money while keeping more deserving technologies shortchanged seems far from a rational strategy.

NOTE II: Tomorrow's power systems and wind's role in them has been the subject of several articles in past issues of Windpower Monthly. The specifics of distributed generation and centralised systems was dealt with in April 1998; wind's role compared with the other renewables in January 1996; and integration of wind into power systems in September 1993. Back issues of Windpower Monthlymay be purchased if available. From 1994 subscribers can access all articles in our on-line archives at www.

Have you registered with us yet?

Register now to enjoy more articles
and free email bulletins.

Sign up now
Already registered?
Sign in