Steve Hodgson Editor, COSPP
The supply of heat is largely ignored in the energy and climate change debate, even though heat represents nearly half the world’s final energy consumption… cogeneration, combined with renewables, is a crucial component of low carbon future. Not my words, but those of the International Energy Agency (IEA), introducing a new report: Cogeneration and Renewables – Solutions for a low-carbon energy future.
The report repeats what could be a very familiar message for COSPP readers: that heat represents 47% of global energy consumption, compared with 17% for electricity, 27% for transport, and 9% for non-energy use, such as fuels used to make plastics. So tackling carbon emissions from heat supplies is perhaps more important than curbing those from power generation. Oil, coal and gas account for more than two-thirds of the fuels used in meeting this demand for heat, and consuming these important resources causes significant emissions of carbon dioxide into the earth’s atmosphere, says the IEA.
The report demonstrates the benefits of high-efficiency cogeneration in meeting parts of that heat demand, and goes on to stress the additional advantages in using renewable sources of energy with cogeneration. Again, this is not news to COSPP readers, who will have noticed the increasing use of renewables with cogeneration in recent issues of the magazine. The twin benefits of renewable carbon-neutral fuels and high-efficiency energy conversion are indeed powerful.
But be careful. The additional benefits of using renewable fuels at high efficiency should not overshadow the very considerable economic and environmental advantages of maximizing the efficiency with which remaining fossil fuels are burnt. And fossil fuels are going to dominate the energy scene for quite a while yet.
However, led by several European countries including the UK, energy strategies are being developed eventually to decarbonize (or largely decarbonize) power generation sectors. Decarbonization is both highly ambitious and, for the foreseeable future, probably impossible.
In a largely decarbonized future, most power is expected to come from carbon-neutral sources – mainly new nuclear plants along with wind and solar sources. But all three are highly intermittent in their own way – nuclear plants need to close down completely for periods of refuelling and maintenance – and will need backing up with large amounts of more predictable technologies, currently seen as gas- and coal-fired power plants, with or without add-on carbon capture and storage technology.
The power generation industry is busy tweaking its generation products, particularly small and mid-scale generators, to maximize their flexibility of operation – and hence their usefulness in balancing intermittent power generators. Employing both gas-fired and renewables-fuelled cogeneration plants to facilitate more low-carbon but intermittent generation onto grids is more complicated – as thermal loads seldom mirror electrical loads – but even better in terms of efficiency. The addition of thermal storage to cogeneration plants can provide the necessary operational flexibility.
Cogeneration has unique benefits with regard to meeting heat loads; renewables-based cogeneration even more so, but gas-fired cogeneration should also take a leading place among fossil-fuelled power generation technologies bidding to aid power grid decarbonization.
Steve Hodgson Editor, COSPP P.S. Please visit www.cospp.com for regular updates on cogeneration and decentralized energy, together with the current issue of the magazine and articles from previous issues. At the same address you can also subscribe to the magazine and sign up for our monthly COSPP e-newsletter.