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This is why Highview has been testing its 300-kilowatt pilot plant for the past nine months, supplying electricity to the UK's National Grid. The process stores excess energy at times of low demand by using it to cool air to around -190 °C. Excess electricity powers refrigerators that chill the air, and the resulting liquid air, or cryogen, is then stored in a tank at ambient pressure (1 bar). When electricity is needed, the cryogen is subjected to a pressure of 70 bars and warmed in a heat exchanger. This produces a high-pressure gas that drives a turbine to generate electricity. The cold air emerging from the turbine is captured and reused to make more cryogen. Using ambient heat to warm it, the process recovers around 50 per cent of the electricity that is fed in, says Highview's chief executive Gareth Brett. The efficiency rises to around 70 per cent if you harness waste heat from a nearby industrial or power plant to heat the cryogen to a higher than ambient temperature, which increases the turbine's force, he says. Unlike pumped-storage hydropower, which requires large reservoirs, the cryogen plants can be located anywhere, says Brett. Batteries under development in Japan have efficiencies of around 80 to 90 per cent, but cost around $4000 per kilowatt of generating capacity. Cryogenic storage would cost just $1000 per kilowatt because it requires fewer expensive materials, claims Brett.

It's no small matter. In fact, Chu says that turning all the world's roofs white would eliminate as much greenhouse gas emissions in 20 years as the whole world produces in a year. But some critics point out that in northern cities, the gain in summer could be outweighed by the loss in winter. The ideal situation, then, would be to get the advantage of white roofs when it's hot and black roofs when it's cold.Now, there may be a way to have both. A team of recent MIT graduates has developed roof tiles that change color based on the temperature. The tiles become white when it's hot, allowing them to reflect away most of the sun's heat. When it's cold they turn black and absorb heat just when it's needed.

Every occupant in a building creates demand for lighting, ventilation, thermal comfort, and electrical power. Lighting, heating, and cooling unoccupied spaces is a huge source of energy waste in buildings, and many studies have shown that building occupancy profiles have a significant impact on building energy use and operational controls. Closer alignment of occupancy patterns to building equipment schedules can be an effective low-cost/no-cost energy efficiency strategy leading to more intelligent control of buildings, a better balance between occupant comfort and energy savings, and lower utility bills. This includes, but is not limited to, HVAC temperature set points, lighting schedules, and economizer schedules.

Decarbonising transport is central to achieving Europe’s policy commitments on climate change. T ransport is expected to deliver a 60% greenhouse gas (GHG) emissions reduction target of the EU for 2050. Achieving these commitments is expected to require a complete decarbonisation of the passenger car fleet. The more ambitious COP21 commitment to limit temperature rises to 1.5°C will also likely demand a complete decarbonisation of transport by 2050.

Attaining a 100% ZEV fleet by 2050 will require all new car sales to be ZEV by 2035 (assuming a similar vehicle life-time as today) and a substantially faster introduction of ZEVs and PHEVs than current policy and likely 2025 policies will achieve .

Compared to the CO2 emission reductions targeted in the current EU plan, the transition to a 100% ZEV car fleet by 2050 will result in an additional reduction of the cumulative CO2 emissions in the period 2020 and 2050 of 2.2 to 3.9 gigatonnes. The current EU White Paper for T ransport, targets to reduce the transport emissions by 60% compared to 1990.