Conservation and Management of Energy Resources

Three ways to manage energy: conserve it, use it efficiently, manage the demand

Managing energy resources starts on the demand side, with the energy nobody has to generate. Energy conservation means using less energy, usually by changing what people do: turning a thermostat down, switching equipment off rather than leaving it on standby, walking instead of driving, or flying less often. Energy efficiency means getting the same useful output from a smaller input of energy: an LED lamp gives the same light as an older filament bulb from a fraction of the electricity, a condensing boiler delivers the same heat from less gas, and an efficient motor drives the same machine from fewer units. Keep the two apart, because a question that asks for ways to reduce consumption usually wants both behaviour and technology, and answers that only list insulation lose marks.

Demand management is the third idea: rather than cutting the total amount of energy used, it changes when the energy is used. Smart meters with in-home displays tell a household which appliance is drawing power and what it costs at that moment; time-of-use tariffs make electricity cheaper at night, so washing machines, immersion heaters and electric vehicle charging are shifted away from the evening peak. Shifting demand matters because the grid has to be built for the busiest half hour of the year, so every unit moved off peak reduces the need for the most expensive and most polluting generating plant, which is usually a gas turbine switched on only to cover the peak.

Reducing demand is usually the cheapest and fastest form of energy supply, because a unit of energy that is never used needs no fuel, no power station, no transmission line and no mining. It also cuts the household bill immediately, which makes it the strategy that reaches fuel poverty as well as emissions. The limit is that the saving is not always as large as the theory predicts. In the rebound effect, money saved by greater efficiency is spent on more of the same service: a car that costs less per kilometre may be driven further, and cheaper lighting may mean more lamps left burning. When efficiency lowers the cost of a service so far that total consumption rises, the effect is known as the Jevons paradox. A judgement about demand management has to acknowledge that rebound reduces the saving but does not usually cancel it.

• Energy conservation: using less energy by changing behaviour, such as lowering a thermostat or travelling less.
• Energy efficiency: the same useful output from less energy input, such as an LED lamp or an efficient boiler.
• Demand management: shifting the time of use away from the peak, using smart meters and time-of-use tariffs.
• Rebound effect: money saved by efficiency is spent on using more of the same service, so the saving is smaller than predicted.

Insulation and energy-efficient devices

In a building, heat always moves from the warm inside to the cooler outside, by conduction through solid materials, by convection in moving air, and by radiation across gaps. Roughly half of the heat lost from an uninsulated house escapes through the roof and walls, and the rest through floors, windows, draughts and ventilation. Insulation attacks each route: loft insulation traps air in a thick fibrous layer on top of the ceiling so that less heat conducts upward, cavity wall insulation fills the gap between the two skins of a brick wall with insulating material and stops air circulating inside it, double or triple glazing holds a sealed layer of air or argon between the panes and a low-emissivity coating reduces radiation, and draught proofing seals the gaps that let warm air blow straight out. In a hot climate the same materials work in reverse, keeping heat out and reducing the electricity used by air conditioning, usually helped by shading and light-coloured roofs.

The principle behind all of them is the same: still air is a poor conductor, so a material that holds a lot of air in small pockets slows the flow of heat. That is why insulation is the first measure to consider and the heat source comes second. Fitting an expensive heating system to a leaky building wastes money, because much of the heat it produces goes straight through the uninsulated fabric.

Energy-efficient devices cut consumption without changing what the device does. LED lighting converts a far larger share of the electricity into light rather than heat; A-rated appliances, heat pump tumble dryers and induction hobs use less electricity for the same job; industrial variable-speed drives and waste-heat recovery cut the energy used by motors and furnaces. Efficient vehicles improve in the same way, through lighter bodies, better engines and hybrid systems, while electrically propelled vehicles replace the engine altogether. An internal combustion engine converts well under half of the energy in its fuel into movement and loses the rest as heat, whereas an electric motor converts most of the stored energy into movement and can recover energy through regenerative braking when the vehicle slows down. The catch is that an electric vehicle is only as clean as the electricity that charges it, so the emissions fall sharply only where the grid itself is low-carbon.

Exploiting existing energy resources, and storing what we generate

One of the cheapest management strategies is to get more out of what has already been built. Exploiting existing energy resources means upgrading plant rather than building new plant: repowering an older wind farm by replacing small turbines with taller towers and much longer blades on the same foundations and grid connection, refurbishing the turbines inside an existing hydro-electric dam, fitting waste-heat recovery to an industrial furnace, or improving the combustion efficiency of a power station that is already running. Because the site, the access roads, the planning consent and the grid connection already exist, the cost per unit of electricity is usually lower and the new environmental impact is much smaller than for a greenfield scheme. The limitation is that it does not change the nature of the resource: extending the life of a gas or coal station keeps carbon dioxide flowing for longer, life extension of a nuclear station depends on passing new safety checks, and repowered wind farms are taller and more visible from further away.

Battery storage solves a different problem. Wind and solar output cannot be turned up when demand rises, so a grid with a large share of them needs somewhere to put the surplus and something to draw on when the wind drops or the sun sets. Grid-scale lithium-ion battery arrays charge when generation is high and prices are low, and discharge into the peak, and they respond to a change in grid frequency in milliseconds, which makes them useful for keeping the network stable. Domestic batteries do the same job at the scale of one house, storing daytime solar output so that a household can use its own electricity in the evening instead of exporting it and buying it back. Vehicle batteries add a third set of storage, either by charging off-peak or by feeding power back to the grid through vehicle-to-grid systems. Pumped hydro-electric storage was doing this long before batteries: water is pumped uphill when electricity is cheap and released through turbines when it is needed.

The limits matter as much as the benefits. Batteries cost a great deal, they degrade with every charge and discharge cycle so their capacity falls over the years, and the lithium, cobalt and nickel they need come from mining that has its own landscape, water and pollution costs. Most grid batteries discharge for only a few hours, which is enough to move energy from midday to evening and to cover a still night, but not enough to cover a windless week or a cold, cloudy winter month. Round-trip losses mean that roughly a tenth of the energy put in never comes back out. Seasonal storage on a national scale therefore has to use other methods, such as pumped hydro, hydrogen or large thermal stores.

Education and transport policies

Education on energy conservation aims to change behaviour, and it works best when it gives feedback rather than just facts. A smart meter display shows a household in real time what each appliance is costing, which is far more effective than a leaflet about kilowatt hours; appliance energy labels and building energy certificates let a buyer compare running costs before they choose; and school and workplace campaigns build habits early. National campaigns can shift a whole culture: Japan's Cool Biz programme asked offices to set their air conditioning to 28°C in summer and encouraged staff to wear light clothing instead of jackets and ties, cutting cooling demand in the hottest weeks without any new equipment. The limit is the gap between knowing and doing. Information campaigns often raise awareness without changing consumption, because the people who pay the bill are not always the people who control the heating, because habits are hard to break, and because a household that understands the problem may still not be able to afford insulation.

Transport policies work by making the energy-expensive choice less attractive and the low-energy choice easier. Road pricing and congestion charging, low emission zones, fuel taxes and higher parking charges raise the cost of driving into a city; investment in public transport, cycling lanes, park-and-ride sites and rail freight gives people an alternative; fuel efficiency standards and subsidies for electric vehicles and charging points change what is on sale. Ground source heat pumps and behaviour campaigns can only go so far if the alternative does not exist.

Two limitations cut across all of them. A charge or tax that falls on driving is regressive, because it takes a larger share of a poorer household's income, and drivers who cannot afford a newer, cleaner vehicle are the ones who pay, which is why such schemes are politically difficult and have provoked protests. And a restriction often only moves the problem: traffic banned from a city centre reappears on the ring road, and emissions rise beside the boundary of the zone. A policy is judged on whether it actually reduced total energy use, not on whether it moved it somewhere else.

Development of new energy resources 1: hydrogen fuel

Hydrogen is an energy carrier, not a fuel that can be dug up: it has to be manufactured, and the way it is made decides whether it helps the climate. It is given a colour to show its origin. Blue hydrogen is produced from natural gas by steam methane reforming, in which methane is reacted with steam at high temperature to give hydrogen and carbon dioxide; the carbon dioxide is then captured and stored underground, which is what makes the hydrogen 'blue' rather than 'grey'. Blue hydrogen uses the existing gas industry, its pipelines, its engineers and its wells, so it can be produced at scale relatively quickly and at a lower cost than green hydrogen today.

Green hydrogen is produced by electrolysis, which uses an electric current to split water into hydrogen and oxygen, and it is green if that electricity comes from renewable resources such as wind, solar or hydro power. No carbon dioxide is produced at the point of manufacture or use. Because it is made from water and renewable electricity, green hydrogen can be genuinely near-zero carbon, and it is most valuable in the uses that electricity struggles to reach: making steel from iron ore without coking coal, producing ammonia and fertiliser, powering ships and aircraft, and long-distance heavy road freight, where a battery would be too heavy.

Both routes have serious limits. Blue hydrogen still begins with a fossil fuel, so gas extraction and transport leak methane, a greenhouse gas far more powerful than carbon dioxide over the short term, and carbon capture never removes every molecule of carbon dioxide, so emissions are reduced rather than eliminated. Extending the life of gas infrastructure can also lock a country into fossil fuel use for decades. Green hydrogen is much more expensive, and it loses a large share of the energy used to make it: renewable electricity is turned into hydrogen, and then often back into electricity or heat, with losses at each step, so it is a wasteful way to do something that a cable and a battery could do directly. Hydrogen is also the smallest molecule there is, so it leaks through seals, is difficult and expensive to store and transport because it must be compressed to high pressure or cooled to a liquid, and it can make steel pipelines brittle. Electrolysis needs large volumes of fresh water and huge quantities of renewable capacity, which can compete for land, water and electricity in the very regions where renewable power is cheapest.

Development of new energy resources 2: ground source and air source heat pumps

Heating is usually the largest single use of energy in a cold country, and most of it is still produced by burning gas. A heat pump changes that by cutting the amount of energy needed rather than the fuel burned. It does not create heat; it moves heat from somewhere cooler into the building, using a small amount of electricity to drive a compressor and a refrigerant cycle, exactly like a refrigerator running in reverse. Because most of the heat delivered comes from the environment rather than from the electricity, a heat pump puts more heat into a building than the energy it consumes. The coefficient of performance (COP) measures this: a heat pump with a COP of 4 delivers 4 units of heat for every 1 unit of electricity, which makes it far less carbon intensive than a gas boiler or an electric resistance heater.

A ground source heat pump takes its heat from the ground. Pipes are laid in horizontal trenches or dropped down vertical boreholes, and a fluid circulating through them absorbs heat from the soil and rock, where the temperature stays at roughly 10-12°C all year round at depth. That steady temperature gives a high and reliable COP, and the system can be reversed in summer to cool the building, passing heat back into the ground. The cost is the installation: boreholes must be drilled, garden or land is needed, and the capital cost is high, which makes it easiest to justify for a new build or a large detached property rather than a city-centre flat.

An air source heat pump takes its heat from the outdoor air, which still contains usable heat even on a frosty day. The unit sits outside the building like an air conditioning condenser, so it needs no land, no drilling and a much smaller installation cost, which makes it the practical option for most existing houses and flats. Its performance is lower and less constant: the COP falls as the outdoor air gets colder, just when the building needs the most heat, and the fan makes some noise that matters in a densely built street.

Both types share the same two limits, and they are the reason heat pumps are not a complete answer on their own. First, they work best in a well-insulated building with larger radiators or underfloor heating, because they run at a lower flow temperature than a gas boiler; retrofitting one into a draughty house with small radiators makes it expensive to run and the household may see no saving at all. Second, they shift demand from gas to electricity, so the climate benefit depends on the electricity supply, and a national switch would raise peak electricity demand at exactly the coldest times unless the grid and the storage are planned for it. The refrigerants used in some units are also powerful greenhouse gases if they leak.

• Ground source heat pump: absorbs heat from the ground through trenches or boreholes, where the temperature is steady all year, giving a high COP.
• Air source heat pump: absorbs heat from the outdoor air; cheaper and easier to install, but the COP falls in very cold weather.
• Both move heat instead of making it, so they deliver more heat than the electricity they use.
• Both need a well-insulated building and low-temperature radiators, and both increase electricity demand.

Weighing the strategies: benefits and limitations

A management answer is judged on the balance between what a strategy achieves and what it costs, and on the judgement you reach at the end. Use the table below to hold the strategies side by side, then decide which comes first for a named place and why.

The strategies that come first are usually the ones that cut demand permanently and pay for themselves. Insulation and efficient devices save energy every year for the life of the building, need no fuel and no new land, reduce bills for the people who install them, and lower the peak load that the grid has to cover. That is why they are the sensible first step in almost any national energy plan, and why they matter most in old, badly insulated housing stock. Exploiting existing resources and repowering continue in the same direction, adding capacity at existing sites with far less new impact.

The strategies that come later are the ones that decarbonise supply, and each carries a conversion loss. Battery storage solves intermittency for hours, not seasons, and its materials must be mined. Hydrogen is best kept for the uses that cannot easily be electrified, because turning renewable electricity into hydrogen and back again wastes much more energy than using it directly. Heat pumps are far more efficient than burning gas, but only in a building that has been insulated first. Education and transport policy change behaviour at low cost but are easy to avoid and can fall hardest on people who have the least choice.

The biggest limits are therefore not technical but economic and social: the upfront cost of a heat pump or a retrofit, the fact that a tenant has no reason to pay for insulation that benefits the landlord, and the argument that a charge on driving takes more from a poor household than a rich one. That is why single strategies rarely work. Efficiency standards make poor equipment illegal; a price signal makes waste expensive; grants and cheap loans remove the upfront barrier; information helps people act; and storage and new sources make the remaining supply clean. A good final judgement names the order, names who pays, and admits what the strategy still cannot do.