The Global Challenge of Energy Use
Across the globe, nearly half of all electricity consumption goes into heating and cooling—whether for homes, offices, industries, or data centers. This huge demand is currently powered mostly by fossil fuels such as coal, oil, and gas. While these sources have supported rapid development for decades, they also contribute heavily to greenhouse gas (GHG) emissions, accelerating climate change.
What makes this even more concerning is that most existing heating and cooling systems are not energy efficient. When fossil fuels are burned directly, they produce 0.6 to 0.85 units of heating for a kWh equivalent of fossil-fuel energy. Similarly, when electricity is used for resistive heating, one unit of electricity produces at most 0.9 units of heat. Carnot cycle, where a refrigerant is compressed to generate heat and expanded to cool, can generate 4 to 5 units of heat and 4 to 5 units of cooling for every unit of electricity. If the output is fully utilised, 10 units of heating and cooling is realized using a unit (kWh) of electricity, implying a Coefficient of Performance (COP)of eight to ten. The Carnot cycle is used in heat-pumps and chillers, but here too mostly either heating or cooling is used throwing away the other to the atmosphere; this halves the COP, as in, for example, in a refrigerator or air-conditioner. To move away from climate change, we require a different approach, where the heating and cooling of a heat-pump and chiller are both utilised, maximising the effective COP. The challenge is to do this in a cost-effective manner, so that heating and cooling from green electricity becomes less costly than that from fossil fuels. The Carnot cycle is old and if this high-effective COP is not commonly used today, it is because the simultaneous use of heating and cooling was far more expensive than the cheap fossil fuels. The impact on climate change was never taken into account in economics.