February 15, 2008
Based on a Discussion Webinar, Friday, 18 January 2008
How best to heat a house is a question that is often hotly debated. On one side, it is a purely personal choice affecting our daily life and personal comfort and productivity. But on the other side, given the enormous amount of heating energy the global built environment is consuming, it is also an important topic in the sphere of social responsibility. Residential heating is an area with great potential for carbon emission reductions.
A new trend due to the widespread discussions regarding climate change mitigation is the design and construction of low-energy houses. What importance does electric heating hold in this new market environment? Electric heating used to be seen as evil by environment-conscious consumers. But are their arguments still valid? Or has the common sense on this topic turned into common nonsense?
Leonardo Energy broached this subject on a Discussion Webinar on 18 January 2008. The following are a few points attracting particular attention that are partly derived from this discussion.
1 ) In low energy houses, the environmental performance of different heating systems converge
The better a house is insulated, the lower its heat demands. If heat demand is low, the environmental impact of the system’s infrastructure becomes higher relative to the impact of the total energy consumption over its life span.
As a result, the environmental impact of an electrical system (high energy impact but low infrastructure impact) converges with the impact of a natural gas system (low energy impact but high infrastructure impact).
2 ) Eco-optimizing the investment
Suppose you have a certain amount of money available for your heating system and you want to invest it in an as environmentally conscious a way as possible. You could invest the entire amount in a natural gas heating system. But in a low energy house, electric heating is cheaper than natural gas by about a factor of four. That leaves you three-quarters of the money which you could invest in extra insulation, or in a renewable energy system generating the required electricity for your heating. To establish which investment will produce the lowest environmental impact for a house, one should execute a Life Cycle Assessment (LCA) for comparable lifecycle cost.
3 ) Electric heating improves comfort
In terms of comfort, electric heating has several advantages over natural gas. It requires little or no maintenance, in contrast to a natural gas system which requires a yearly check of the boiler, a regular cleaning of the stack, and regular purging of the pipes as well as the probability of a water pump replacement at least once during the life of the system.
Electrical heating also beats natural gas in terms of safety. There is no risk of gas leaks, CO production from burners, or boiler explosions.
Furthermore, an electric heating system saves space, since it doesn’t require a boiler and water tubes, and electric radiators are smaller than those of a central heating system.
4 ) Electric heating: base load or peak load?
During the discussion, attention was drawn to the fact that the carbon emissions of electricity depend on the country as well as on the time of use. Peak load electricity typically has a higher CO2 emission than base load. Electrical heating is mostly used in winter periods with peaks in the morning and in the evening. These peak hours correspond in electricity production with peak power or semi-base load generation. As a result, a newly installed electrical heating system for a home in France would typically use electricity generated by a mix of 67% natural gas, 13% coal, 10% oil, and only 10% nuclear. This partition results in CO2 emissions for electrical heating of around 600 g/kWhe, which is more than twice the emissions from gas heating.
Electrical accumulation heaters that are used in an efficient manner can counter the above issue, if they are programmed correctly and loaded during the night when electricity production is on base load.
In a house with a very low energy demand, hot water production will consume more energy than the actual heating system. If the hot water boiler has a buffer that is large enough, it can be programmed to function only during the night and will consume base load power only.
5 ) A passive house as a means of energy storage
In combination with smart metering techniques, passive houses could be used for peak shaving. Indeed, since these houses are very well insulated, they loose their heat very slowly. A short power outage will have almost no influence on the temperature inside the house. This means that the heating in a passive house could be remotely switched off during power peaks on the grid.
This case is even more persuasive if the passive house makes uses of electric accumulation heaters. Such heaters can be loaded during the off-peak hours and disconnected from the grid during peak demand.
In the future, the combination of a passive house with a plug-in electric vehicle might provide even more options to balance the grid.
6 ) Who is going to produce the additional electric power?
A comment was made during the discussion on the availability of electrical energy in the upcoming years. If the share of electricity in heating systems increases, this will result in a notable increase in total electricity demand. But somebody will have to produce this electricity. In the case of the UK, old nuclear power plants are being shut down and the new generation of nuclear power plants will only be ready in ten to twenty years. A shortage in electricity production is expected to grow during the gap between those two ‘nuclear eras’. Is it sensible to promote electric heating during this period of shortage?
On the other hand, if nuclear power production decreases, natural gas power production will probably increase. Those power plants share the purchasing market for their fuel with residential buyers owning a natural gas heating system.
7 ) Future alternatives: biomass and hydrogen
In the medium term future, other heating systems might be developed to compete with both natural gas and electric heating. Examples are biomass and hydrogen. Biomass has the disadvantage that it competes with food production and forest conservation for land use. Hydrogen has the disadvantage that it would require a whole new infrastructure for the distribution of the fuel, comparable with what was build for natural gas a few decades ago.
8 ) A suitable energy carrier for carbon management
As a final conclusion to the discussion, virtually all participants seemed to agree on the fact that we can’t rely on a single system. Keeping a portfolio of various fuels and systems available is the most probable and indeed, even the preferable way forward.
Electricity has the advantage that it is a very flexible energy carrier. It can be generated either locally or centralized by many different technologies (solar, wind, nuclear, natural gas with cogeneration, etc.), and it can be used in many different heating systems (electric radiators, floor heating, heat pump, electric boiler, etc.). This makes it a suitable energy carrier for carbon management.