Energy consumption and water supply

Overview

How energy use in urban buildings can be reduced, district heating and combined heat and power and fuel poverty.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Why does energy consumption matter so much to urban sustainability?

   Model answer

   Because it is the source of most of a city's greenhouse gas emissions and much of its air pollution, so it drives the environmental dimension directly. It also drives the social dimension, because the cost of energy determines whether households can keep warm, and because emissions from heating and traffic damage the health of those living beside busy roads. And it drives the economic dimension, through the cost of fuel to households, businesses and the council, and through security of supply. Energy therefore links all three strands more tightly than any other single issue.

2. 2

   Explain how energy use in urban buildings can be reduced.

   Model answer

   By retrofitting the existing stock, which is where most of the demand is: loft and cavity or solid wall insulation, double or triple glazing, draught-proofing and airtightness with controlled ventilation, insulating pipes and tanks, and upgrading heating controls. By replacing inefficient boilers with heat pumps or connecting to district heating. By using LED lighting and efficient appliances. In new build, by orientation and window placement for passive solar gain, high levels of insulation, and the compact terraced and apartment forms that lose less heat per dwelling than detached houses. Behind these sit the policy tools: building regulations for new work, energy performance certificates at sale and letting, minimum standards for rented property, grant and loan schemes for retrofit, and smart meters and tariffs to make consumption visible.

3. 3

   What is district heating and combined heat and power, and where do they suit?

   Model answer

   District heating supplies heat from one central source through a network of insulated underground pipes to many buildings, which then need no individual boilers. Combined heat and power generates electricity and captures the heat that a conventional power station would reject to the air or a river, raising the useful output from the fuel very substantially. The heat source can be gas CHP, an energy from waste plant, large heat pumps, biomass or industrial waste heat. They suit dense areas with a high and steady heat demand close together, such as flats, hospitals, universities, offices and new estates built with the network in place. The obstacles are the very high capital cost of laying the network, the disruption of retrofitting pipes into existing streets, the need to sign up enough customers to make the scheme viable, and the fact that customers are then tied to a single supplier.

4. 4

   How can renewable energy be used within a city, and what limits it?

   Model answer

   Solar photovoltaic panels and solar water heating on roofs; air source, ground source and water source heat pumps; small wind turbines on exposed sites, though rarely efficient in the turbulent air of built-up areas; energy from waste and landfill gas; biomass boilers; and biogas from sewage treatment and food waste digestion. The limits are the amount of suitably oriented, unshaded roof space, particularly for flats where the roof serves many households; restrictions in conservation areas and on listed buildings; the cost and capacity of grid connection for exporting power; intermittency, which means storage or a grid connection is still needed; and split incentives, where a landlord pays for installation but the tenant receives the saving.

5. 5

   What is fuel poverty, and why is it a sustainability issue rather than only a welfare issue?

   Model answer

   Fuel poverty describes households that cannot afford to keep their home adequately warm, arising from the combination of low income, high energy prices and, critically, an energy-inefficient dwelling. Its consequences are documented in cold-related illness, respiratory and cardiovascular problems, mental health effects, and excess winter deaths, concentrated among older people and young children. It is a sustainability issue because the cause and the remedy are the same as for emissions: the least efficient homes are both the most expensive to heat and the most polluting, so insulating them cuts carbon and cuts hardship at the same time. It also shows why the social and environmental strands must be planned together, since a policy that raises energy prices to reduce demand will deepen fuel poverty unless retrofit reaches those households first.

6. 6

   How does the planning of a settlement reduce transport energy use?

   Model answer

   By shortening trips and making the alternatives to driving realistic. Mixed-use development puts shops, schools, workplaces and homes close together so daily needs can be met on foot. Higher densities, concentrated around bus corridors, tram stops and stations, put enough people within walking distance to make frequent services viable. A connected network of direct walking and cycling routes makes short trips quicker than driving. Limiting the parking provided with new development, through maximum rather than minimum standards, reduces car ownership and use. Locating employment and large trip generators where public transport already runs, rather than on ring roads, prevents new car dependence being built in for the lifetime of the buildings.

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