London produces 44 million tonnes of CO2 per annum. The GLA proposes to reduce this by 7.7 Million tonnes from London’s housing by 2025, as part of an overall 80% reduction by 2050. This means that either 80% of homes and businesses become zero CO2 in that period, or all homes and business achieve an 80% reduction in their CO2 emissions.
In recent years an average of 25,000 homes has been built in the capital every year, and there is no reason to expect a radical shift in this number. Demographic studies tell us that from 2016 to 2050 we will need to achieve 17-21% growth in the total homes in the capital, adding around a million new homes to the current three million. If these were built to current standards they would add to the total CO2 and make matters worse. The Code for Sustainable Homes legislation will ensure that by 2016 these have to produce zero CO2. . However, the energy used in and by our homes only accounts for 60% of the average households footprint, so even if these are zero carbon using the Code for Sustainable Homes definition[i] , each home will produce an additional 40% of the average homes CO2 output which will add to the CO2 burden of the capital. This amounts to an additional four tonnes per household or a total of 100,000 tonnes CO2 per annum. What remains to be tackled is the enormous burden of the CO2 produced by the capitals inhabitants’ use of energy for transport and aviation.
Existing Housing Stock
The majority of the capitals housing stock dates from before the First World War (26%) or between 1918-1944 (32%). These buildings can be upgraded by adding insulation to the fabric, insulating the roofs, external walls and replacing the windows with high performance versions, but most of these are built with solid external walls and either no cavity or one with old and highly suspect wall ties requiring expensive remediation.
Upgrading will be very disruptive to the use of the stock as it requires complete internal refurbishment which usually only happens every 50 years or so, waiting for this to happen ‘naturally’ will mean waiting a few hundred years, unless there is a legal or fiscal imperative to carry out the works sooner. High energy prices or the UK equivalent of Hurricane Katrina may do the trick. The alternative to this is to wrap the fabric in a warm blanket by applying external render over insulation. This would be unpalatable to the majority of people. The irony of the situation is that in order to reach the target we are aiming for we may have to change dramatically that which we are trying to preserve. This dichotomy is being played out wherever there is an objection to a planning application for a wind turbine in the countryside. At what point will it seem sensible to take this step I wonder, when the Thames is lapping around our ankles? Or will we wait until it reaches our knees?
An alternative strategy would be to decarbonise the energy supply to London. This means that we make major strategic changes to the energy supply to London, to the extent that whatever energy the capital is using it is not contributing to its carbon footprint. To some, this may seem counterproductive, and suggests that it is acceptable to continue to waste energy, but what we need to do, is to stop burning fossil fuels to generate our energy firstly, and waste less of it secondly. Since carbon neutral power sources, by definition, do not add to the sum of CO2 in the atmosphere we will not be making the situation worse.
By decarbonising the energy supply to the capital we will enable us to space out the energy efficiency upgrades of the stock over a more realistic period.
What are our options for upgrading the capitals energy supplies?
It is fairly safe to say that nuclear is not going to be part of the answer, so what is?
High density living means that applying either solar thermal or photovoltaic cells across the stock will be insufficient; it will be helpful, but not enough to solve the problem. A simple calculation shows that there is not enough roof space in the average London street to power the amount of energy use being consumed by the same street. There simply isn’t enough roofscape to fit enough solar cells to power any city, and the power is not available at night when cities need a lot of it. That’s leaving aside the difficulties of actually retrofitting such systems elegantly to the variety of available roofscapes, and dealing with the inevitable planning issues.
Wind power in an urban location has been pretty much kicked into touch by now, a combination of noise problems, vibrations and the visual problems all contribute to the general acceptance that wind energy is best left on the farm, a big wind farm, preferably offshore.
Wait a minute, London is near the sea, and permission was recently granted to the London Array, an offshore wind farm in the Thames Estuary which will power 250,000 homes with zero carbon electricity. So that will deal with deal with the CO2 emissions from the electrical energy of about 8% of London’s stock, and this is set to be the largest wind farm in the world. We need another twelve just for London.
Solar thermal heating is proving to be among the most cost effective renewable technology, and it is the only one that tackles heat rather than electricity. But its application in an urban location is plagued by the same issues as photovoltaics, how to apply them satisfactorily on a large scale to existing buildings. There are no easy answers to this. Façade and roof space is limited at high densities.
The value of CHP
CHP is being touted as the best solution to a low and zero carbon energy system for urban locations.
The use of CHP in all the new stock being built currently and in the foreseeable future will be required anyway, because compared to the current National Grid, CHP is about twice as efficient, effectively halving the CO2. So the question is really, how can we apply zero carbon CHP systems across the capital? The answer, at present, seems to be: not easily.
The first contender in the zero carbon corner is biomass. There is unlikely ever to be a sufficient supply of biomass fuel available to power the capitals energy generators.
A question that is often asked about biomass and other energy crops is whether there will be a limited amount of fuel, and whether its production will drive up the costs of other crops due to competition for arable land. Many studies have been done on this[ii], and conclude that biomass type crops can contribute around 10% of our total energy requirement. As for the land issue, we are currently not using 640,000 Ha of arable land in the UK because if we were to do so we would overproduce. This land could be used for energy crops, or other low grade land currently being used for food crops can be diverted to energy crops and the set aside land used for food crops. The use of recycled paper means that the demand for wood pulp has fallen, and the large amount of forestry planed in the 60’s and 70’s is maturing, the supply of UK produced low grade timber is going to outstrip current demand by a significant amount.
The question remains whether biomass is a practical energy system for use in dense urban environments. Two crucial problems have to be tackled, the amount of fuel storage required and the pollution emanating from the combustion of biomass.
In any urban site giving valuable area over to storage of energy supplies is an expensive loss of what would normally be useable and profitable area. This, coupled with the requirement to have parking space for large delivery vehicles can make its use unfeasible, where there are alternatives.
The alternatives are :
Waste to energy systems, which burn the waste the capital produces and turn it into heat and energy, either though direct waste to heat by burning the material, or first by turning it into gas and then burning the gas in conventional CHP systems. The latter alternative is attractive because the technologies to burn gas in CHP systems are well understood, and there is already a complete gas network. The first such plant is under construction at Park Royal, West London.
Biofuels, which have been suffering from bad press recently, is a viable alternative. The questions about its viability centre mainly around the fact that the production of biofuels may produce more carbon than is produced by consuming a similar volume of fossil fuels, i.e. we are inadvertently making matters worse by using biofuels. This problem notwithstanding, should biofuels prove to be carbon neutral, then they are much more appropriate to urban use for a few reasons. Firstly because the amount of energy stored in the fuel is far greater than in biomass, so a smaller volume of the fuel is required to provide the same amount of energy; and secondly because the fuel can be piped over longer distances, so deliveries are not required to arrive wherever the CHP system is located. Biomass pellets can also be piped, but over shorter distances, and more frequent deliveries would still be needed.
To conclude, the problems confronting the delivery of the targets set for London appear to be insurmountable. They are not, but the current economic framework we are operating in is not conducive to the targets being met. There is no economic imperative to upgrade the existing stock, and the legislation covering new stock is in its infancy. There is a great deal of uncertainty in the housing market about what renewables technologies are best applied where. There is a poor relationship between energy policy and construction policy; we need to work quickly to bring these two industries into sync so that what works for one will work for the other.
[i] Zero Carbon is where a residential development produces as much energy annually as it uses annually
[ii] Royal Commission on Environmental Pollution: Biomass as a renewable Energy Source