A guide for understanding how cities can be more energy efficient is being launched this week.

Understanding the impact that biomass burning stoves in rural Kenya are having on the environment and models that enable planners to plot a path for reducing carbon dioxide emissions in cities are some of the topics covered in a new textbook, developed by academics from Imperial College London.

The book, ‘Urban Energy Systems: An Integrated Approach’, is edited by Imperial’s Dr James Keirstead and Professor Nilay Shah. It brings together the major lessons learnt from a £4 million, 5-year collaborative project with BP that investigated the technologies and systems used in cities to distribute and consume energy. Understanding these systems in more detail can provide valuable insights into how to make the distribution and consumption of energy more cost effective and sustainable in cities in the future.

Understanding how urban areas in Kenya consume energy is the focus of one of the studies in the book

Professor Nilay Shah, from the Department of Chemical Engineering at the College, says: “Cities use up approximately three-quarters of the world's energy and play a major role in issues such as economic security and climate change. Our book features a mix of case studies, modelling techniques, and background materials that can help the next generation of engineers and policy makers take new approaches to designing our urban energy infrastructure so that it is more efficient and has less impact on the environment.”

In the book the researchers covered case studies on cities around the world including London, Copenhagen in Denmark, and Nakuru, which is the fourth largest city in Kenya.

One case study covered the evolution of London’s urban energy system and examines how this system has evolved in response to a range of issues including the needs of the population, the promise of technological innovations and the environmental and economic impacts of energy consumption.

London’s energy infrastructure began as a group of highly fragmented local industries. For example, by 1918 there were 70 authorities, 50 different types of electrical and gas systems, 10 different electrical frequencies and 24 different supply voltages.

Dr Keirstead, co-author from the Department of Civil and Environmental Engineering, says:

“At the turn of the twentieth century it would have been impossible to take a light bulb from the west end and plug it into a socket in the east end of London. This is because the energy market was so fragmented with many different suppliers and ways of distributing energy to homes.”

However, during the interwar years, the Government consolidated the network into one national energy grid, which enforced uniformity in the way that energy was generated and distributed. By the 1980s, the system changed again and the Government privatised the national grid. Now, six big energy companies dominate the market. 

The evolution of London’s energy system was also influenced by other factors affecting the UK such as the discovery of resources. The development of North Sea oil and gas deposits in the 1960s enabled large power plants to be built in remote areas that could run on natural gas, which was a cheap and abundant energy source at the time. However, as natural gas resources begin to run out the national grid faces a range of challenges including an increasing reliance on imports, which is ultimately impacting on costs for consumers.

Denmark’s energy infrastructure took a completely different approach to London. External shocks  such as the Oil Crisis of 1973, where an enforced ban from petroleum producing countries in the Middle East caused an oil shortage and rising costs, forced planners in Copenhagen to re-evaluate how they used, generated and supplied their energy city-wide.

They implemented a policy that enforced the adoption of combined heat and power plants. This technology captures waste heat generated during power production and puts it to use, mostly to supply hot water and heat in city districts. Consequently, Copenhagen is now one of the most energy efficient cities in the world.

In contrast to London and Denmark, cities in less developed countries are faced with an entirely different set of challenges. In the book the editors did an analysis of changing energy consumption and environmental impacts in the Kenyan city of Nakuru spanning a 30-year period.

The first study, published in 1980, warned of severe de-forestation in the surrounding area in Nakuru because of an over reliance of households on biomass, which include wood, charcoal and animal wastes that are used for heating and cooking.  The study suggested that a move to electricity production could take the pressure off the environment.

The second study in 2010 found that while technologies had improved - such as the introduction into homes of a more efficient biomass burning stove - de-forestation continues to put pressure on the environment. This is due to the rising population, which has grown from 17,000 households in 1980 to 123,000 in 2010. The team found that even though homes were being more fuel efficient, the shear growth in their number was putting added pressure on the environment.

The researchers in the case study also analysed why more homes had decided to buy efficient biomass burning stoves instead of connecting to the electricity grid. They discovered that the barrier was cost. Connection to the grid has an up-front fee of $US450, whereas an efficient biomass stove costs between $2 and $3, which is much more in line with the spending power of Kenyan households that can earn roughly $4 per week.

The researchers also found that even if wealthier homes did connect to the electricity grid, their biomass consumption remained relatively the same due to traditional cooking methods. This debunked previous theories that suggested richer households used more sustainable resources the higher they moved up the energy ‘food chain’.

The academics also looked at ways to encourage residents in Nakuru to adopt more sustainable practices that are cost effective and in line with their cultural traditions. One concept they devised was getting households in the local vicinity to share costs of purchasing a communal anaerobic digester, which produces clean gas for cooking from household waste.

The team also carried out a modelling technique to show how Newcastle-upon-Tyne can meet their share of 2050 targets, where the UK reduces carbon emissions by 80 percent. The modelling tool takes forecasted energy demands and selects the energy technologies that meet a specified carbon emissions reduction target at the minimum cost. In thousands of simulated future scenarios the model showed that basic efficiency measures such as loft and cavity wall insulation make an important difference to energy efficiency.  The researchers say their scenario should give local authorities confidence to act now and incentivise households to adopt these efficiency measures.

Dr Keirstead concludes: “This book will give urban planners, engineers, urban authorities and national and international energy policy makers a valuable resource that we hope will make our cities more liveable and affordable.”