Professor David Elliott (front left) answers questions about renewable energy from the audience at Staffordshire University's Ruxton lecture theatre.
Renewable energy technologies, such as wind, solar, and tidal power are our best bet if we are to tackle the twin threats of climate change and dwindling fossil fuel reserves. This was the message delivered by energy technology specialist Professor David Elliott in a talk at Staffordshire University held on 12 November 2014. Drawing on his many years in industry and academia, he made a considered and objective case for a UK energy policy that gives much greater emphasis to renewables rather than building more nuclear plants. The technologies are already there, as his talk amply illustrated; all we need is the imagination and political will to make the shift.
More energy than humanity will need!
The Sun is a huge and ever present source of energy - able to supply many times more energy than humanity will ever need. Fossil fuels are likely to start running out, but in any case their use is leading to irreparable damage to the climate. As for nuclear power, plants are costly to build, they pose major issues around safety and security, and their uranium fuel is also a finite resource. Removal of carbon dioxide from power station flue gases using carbon capture and storage is very expensive and itself requires considerable energy. Unconventional sources such as shale gas are only short lived, and not part of any long-term solution. That, according to Professor Elliott, requires immediate and sustained investment in a range of renewable technologies.
Britain can generate 80% of its energy from a mix of renewable sources by 2050, argues Professor Elliott
Renewable energy options
Hydro, geothermal and solar thermal
He went on to consider the current range of available options, led by hydro. This has been generating power for decades, and in some countries all their electricity comes from hydro schemes. But hydro dams and resultant lakes often have a big impact on their locality, and can even be a source of methane from rotting vegetation following flooding of an area. Geothermal, a form of 'natural nuclear energy' from deep underground, can be exploited, for example for combined heat and power, but only in particular sites. Solar thermal energy is apparently 'big in China', where the hot water from large-scale schemes can be stored and used for district heating. It is now quite feasible to store heat captured in summer in underground heat stores for use in the winter.
Solar PV and CSP
Solar PV for electricity is growing rapidly, with global capacity now more than 130 gigawatts (GW). Germany alone accounts for 37 GW, compared with just over 4 GW in the UK. Its merits are flexibility, reliability and silent, smell-free operation! But of course it doesn't work at night! Another way of harnessing the sun is 'concentrated solar power' or CSP. This uses an array of mirrors or lenses to focus the sun on a collector that converts the light to heat to drive a turbine, or channels it to a heat store for use at night. These naturally work best in sunnier climes than the UK, but power from CSP plants in north Africa, for example, could one day be distributed to northern Europe via a supergrid.
Biomass contributes 35% of total renewable electricity production in the UK at present, and is also a major source of renewable heat. It is theoretically carbon neutral, but there can be a considerable delay - perhaps decades - while absorption of CO2 by growing plants offsets that released during combustion, particularly with slow-growing biomass such as timber. Also, biomass needs land to grow, land that often should be growing food instead.
Wind energy seemed to hold a special appeal for David Elliott. 'I could happily gaze at a wind turbine in operation for hours' he claimed, admitting that not everyone shared his taste in pastimes! Onshore wind turbines are often controversial , but Britain has massive potential for offshore wind, and despite the greater cost compared to onshore schemes, the offshore operational capacity could increase sixfold to more that 30 GW if all current projects come to fruition. This compares with the 360 GW currently generated by wind energy around the globe.
Wave and tidal power
Big technical and engineering challenges face attempts to tame wave energy, but tidal power is a different proposition. Massive schemes such as the long mooted Severn Barrage are hugely disruptive to the environment, so instead attention has turned to developing smaller, more flexible tidal power technologies, such as tidal lagoons and underwater tidal turbines. Arrays of the latter distributed around the UK's coastline would overcome the problem of intermittency associated with tidal power - it only works when the tide is running!
The issue of intermittency
Advocates of renewables are used to facing the problem of intermittent operation - how to supply power 'when the wind don't blow and the sun don't shine'! The solution, according Professor Elliott, comprises a mix of strategies, including:
- cut demand by improving energy efficiency;
- ensure a good mix of generating technologies
- use gas-powered plants as short-term back up to meet surges in demand or dips in supply
- store surplus electricity by pumped storage into hydro reservoirs or through production of hydrogen or methane ('methanation') fuels;
- connect regions of Europe and elsewhere by supergrids to distribute power from areas with surplus to those with a shortage
Surplus electricity from wind turbines, like this one on the outskirts of Stafford, can be used to produce hydrogen or methane fuels.
The UK situation
Why is the UK lagging behind its European neighbours in terms of renewables, when it has such good resources of wind and tidal power? Like many others, Professor Elliott expressed his frustration over our lack of any clear long-term national strategy for renewables. Instead the government is attempting to lure the nuclear industry to invest in the UK with promises of guaranteed prices for electricity.
Cheaper in the long run
But, he warned that the ever falling cost of renewables would make them a cheaper option by the time any new nuclear plants come on stream in the UK. An exercise in 2013 for the UK Pugwash group set out a pathway for a high renewables scenario that by 2050 could cut carbon emissions by over 80%, meet demand at all times, and cost slightly less than alternative scenarios containing nuclear power.
Anticipating how energy generation in the UK might evolve in the next decade, Professor Elliott was critical of the current Renewables Obligation, and also of its replacement, the competitive 'Contract for a Difference' (CfD) system that will replace it from 2017. This is likely to prove bureaucratic and costly, he predicted, favouring large-scale generators at the expense of small to medium-sized players. Again, he contrasted this UK system with that in other European countries such as Denmark and Germany, where there was much greater community ownership of renewables, and hence more local control of energy supply.