BraveNewClimate

Guest Post by Martin Nicholson. Martin studied mathematics, engineering and electrical sciences at Cambridge University in the UK and graduated with a Masters degree in 1974. He has spent most of his working life as business owner and chief executive of a number of information technology companies in Australia. He has a strong interest in business and public affairs and is a keen observer of the climate change debate and the impact on energy. He is author of Energy in a Changing Climate, as well as an upcoming book on sustainable energy systems, and is the lead author of the 2011 paper in the journal Energy “How carbon pricing changes the relative competitiveness of low-carbon baseload generating technologies“. He wrote a popular post last year on BNC entitled: Cutting Australia’s carbon abatement costs with nuclear power

This post, and the one to follow, provides an insight into Martin’s new book: The Power Makers’ Challenge: and the need for Fission Energy

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PART 1

Introduction from the Book Cover

“The Power Makers – the producers of our electricity – must meet the demands of their customers while also addressing the threat of climate change. There are widely differing views about solutions to electricity generation in an emission constrained world. Some see the problem as relatively straight forward, requiring deep cuts in emissions now by improving energy efficiency, energy conservation and using only renewable resources. Many electricity industry engineers and scientists see the problem as being much more involved.

The Power Makers ’ Challenge: and the need for Fission Energy (http://dx.doi.org/10.1007/978-1-4471-2813-7) looks at why using only conventional renewable energy sources is not quite as simple as it seems. Following a general introduction to electricity and its distribution, the author quantifies the reductions needed in greenhouse gas emissions from the power sector in the face of ever increasing world demands for electricity. It provides some much needed background on the many energy sources available for producing electricity and discusses their advantages and limitations to meet both the emission reduction challenge and electricity demand.

By analysing the three main groups of energy sources: renewable energy, fossil fuels and fission energy (nuclear power), readers can assess the ability of each group to meet the challenge of both reducing emissions and maintaining reliable supply at least cost. It is written for both non-technical and technical readers.”

Synopsis

Greenhouse gas (GHG) emissions are changing the landscape for our Power Makers – those good folks that deliver our ultra-reliable electricity supply.

The Power Makers have been largely reliant on fossil fuels for providing abundant and relatively cheap energy and delivering a high standard of living in developed countries. Even so, more than a third of all humanity still has no access to electricity. For those living in less-developed countries, their long-term aspirations are to achieve the same high standard of living enjoyed in the developed world. That means access to abundant cheap energy – and much more of it!

The mainstream scientific consensus is that GHG emissions are the primary cause of recent global warming. In addition, fossil fuels are a finite resource. Continuing to use fossil fuels as our main energy source for generating electricity could lead to both an energy supply and climate disaster: two good reasons for migrating our electricity generation away from fossil fuels.

Technically, economically, socially and politically – we face many challenges in trying to harness non-fossil-fuel energy on a large scale.

The challenge facing our Power Makers is to maintain a reliable, cost effective electricity supply with substantially less emissions. With over 65% of our electricity currently coming from fossil fuels (coal, gas and oil) that produce 44% of the world’s GHG emissions, this is no small challenge. The Power Makers have no choice but to clean up the fossil fuel power plants (or replace them) while maintaining the supply security paramount for both Power Makers and their customers.

 Renewable energy is popular as a low emission replacement for fossil fuels. It took immense geological pressure over millions of years to create those energy-rich stores of fossil fuels like coal, oil and gas from plant matter. Conversely, most renewable energy sources are relatively dilute and variable in supply. Exploiting renewable energy sources in similar ways to fossil fuels is proving to be difficult and expensive.

The Power Makers face many questions. What are the implications of harnessing such diffuse energy sources? How do they ensure electricity supply security with energy flows that are variable and intermittent – sometimes delivering a lot of power, sometimes a little, and at other times none at all? What methods can be used to store large amounts of energy to cover the non-generating periods? Is nuclear energy a clean and sustainable alternative? What are the costs and timescales required for a major energy transition? I consider all these questions in my book.

The Carbon Challenge

At the 2009 Climate Summit in Copenhagen the main point of agreement among the world’s leaders was that the target temperature rise should be no more than 2ºC above pre-industrial levels. To achieve this the IPCC tells us we must reduce GHG emissions by 85% by 2050, world-wide.

On average across the world, about 500 kilograms (kg) of CO₂ equivalent are produced for every MWh of electricity generated. This is known as the ‘emission intensity’. In Australia, the emission intensity is almost twice as high as the world average. To reach the emissions reductions needed by 2050 several studies have shown that the average emission intensity needs to be reduced to as low as 50 kg CO₂-e/MWh. Current estimates for the emission intensity of very low-carbon fossil fuel plants using carbon capture and storage (CCS) vary from 100 kg to 250 kg CO₂-e/MWh depending on the technology. This may mean that there will be little place for fossil fuels by 2050.

Renewable Energy

There are many renewable energy options including wind, solar, hydro, biomass, geothermal, tidal and wave. Some are better at producing reliable electricity than others. Unfortunately all of these resources have relatively low energy density, so a substantial amount of the resource needs to be captured to generate the quantity of electrical energy needed. A dilute resource also means much greater cost to extract the energy and convert it into usable and reliable electricity.

Some of these renewable options are not only very dilute but variable – not there all the time when you need them. This does not imply there is no place for renewables but it does indicate that renewable sources may not readily replace significant amounts of coal power, which will be required to reduce the emission intensity to the levels needed.

What the Power Makers need are energy sources that can produce a predictable amount of energy as and when it’s needed – not at the whim of nature. Three renewable technologies are considered to be reliable, proven and commercially established but may be constrained by the availability of resources; water (hydroelectricity), geothermal hot water (or steam) and combustible biomass. Concentrated solar power (CSP) with heat storage is proven technology but is currently expensive and still only being constructed on a relatively small scale. Intermittent wind, solar PV and wave technologies could also replace fossil fuels if sufficiently large-scale energy storage was available.

Energy Storage

Pumped hydro storage (PHS) has been used for almost as long as electricity networks have existed. In Australia we have about 20 GWh of PHS. If we wanted to get all of our electricity from renewable energy, we might need at least one full day’s storage to handle variability. Australia consumes on average about 700 GWh per day so relying on PHS alone would mean increasing our PHS capacity 35 fold.

PHS systems need large areas of land for the reservoirs (although the ocean could be the lower reservoir) and the upper reservoir needs to be as high as possible, usually a head of more than 200 m above the lower reservoir. The smaller the head, the larger the reservoirs need to be. These geographical requirements limit the number of suitable locations and environmental issues will need to be considered.

Another storage option is compressed air energy storage (CAES). As with PHS, CAES requires suitable geological sites. CAES sites ideally already contain disused mines, gas/oil fields, aquifers or salt domes that can be used as compressed air storage areas. Existing CAES plants are few and small (under 3 GWh) so we might need over 200 such locations for Australia. Similar situations for both PHS and CAES exist elsewhere in the world.

Other storage options include hydrogen and various types of batteries. These are significantly more expensive per MWh than open cycle gas generators: one of the reasons they are not more widely used today. Hydrogen storage systems are still under development, so difficult to cost with any accuracy.

It is clear from the above that we really only have a few limited, scalable options for electricity storage. This is a field that has attracted a great deal of interest over the past few decades. Improvements in battery technology are progressing and developments are taking place in both CAES and hydrogen storage. But there are some chemical and physical limitations that will restrict future size and cost reductions.

Clean Coal

Coal is the major energy source for the world’s electricity. It is relatively easy to mine, transport, store and convert into electricity. This makes it the cheapest source of electricity today. What may kill coal is its GHG emissions. The world is seeking advanced coal technologies that can clean up the plants to help deal with the emissions problem.

Over time, significant improvements have been made in coal conversion efficiency. This means less coal is used to generate electricity. Modern advanced ultra-supercritical plants are over 50% more efficient than the old solid fuel burners used in the first few decades of the last century. Gasifying coal could almost double the efficiency of those very early plants but even with these efficiencies, coal will still be too emissions intensive.

Carbon capture and storage (CCS) is a set of technologies that could significantly reduce CO₂ emissions from new and existing coal and gas power plants. The CO₂ is captured at the power plant and transported to a suitable long-term storage space, which would generally be underground in depleted oil or gas reservoirs, discarded coal beds or well-capped aquifers.

Capturing the CO₂ is a costly and energy intensive process. For a pulverised coal plant it can use as much as 40% of the total electricity generated. On cost alone, it seems unlikely that CCS will be implemented within the next two decades without financial incentive above and beyond the likely carbon price. In other words, without government subsidies, it will be cheaper for the Power Makers to continue releasing CO₂ than invest in costly CCS technology.

Baseload Alternatives

Today, most baseload demand is met by coal plants. To replace coal plants we need technologies that can service baseload – the minimum amount of power required to meet expected customer demand. Typically, baseload power stations run continuously to meet this demand throughout the day and night.

Fig. 2.1 750 MW generator with two steam turbines. From Campbell (1993)

Baseload plants need to have high reliability with low forced outage rates and high capacity factors. Coal, gas, nuclear, geothermal and biomass meet these criteria. The first three are considered to be non-renewable and the last two renewable sources of energy. In some countries like Norway and Canada with access to plenty of rain and snow melt, hydro plants are also be used as baseload plants.

Biomass and conventional geothermal plants are both resource-constrained. Biomass needs huge areas of land to grow fuel for a large plant to run throughout the year. Conventional geothermal, using surface or near-surface geothermal heat is already significantly exploited in most of the lucky 24 countries blessed with hot near-surface reservoirs, so the scope for further coal replacement with conventional geothermal is limited.

From MIT except Wind from NREL, Hydro and Nuclear (author calculation) , Biomass from Ragland

Solar thermal with thermal storage and/or gas co-firing might be a candidate in some solar belt countries, but at significant additional cost today. Typically, electricity from solar thermal is two to three times the price of coal power and will probably be restricted to servicing afternoon peak rather than baseload. Engineered Geothermal Systems (EGS) that target very deep hot rock strata may also be a candidate – if we can ever get them to work on a commercial scale.

Some countries have already started what is called the “Dash for Gas” to replace dirty coal plants with ‘clean’ gas. Others will follow. They consider that gas will get them on the track to reducing emissions from electricity generation. Eventually, they will inevitably have to look for alternatives if they are to make the 2050 emissions reduction target discussed earlier.

That brings us to nuclear power. Nuclear is a strong baseload candidate to replace coal as it has in France over the last 40 years. It also happens to have an emissions intensity well under the 50 kg CO2-e /MWh – the goal we are aiming for in 2050.

CONTINUED IN PART 2

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Filed under: Emissions, Nuclear, Renewables