Heat Pumps and Heat Recovery: A Comprehensive Approach to Decarbonization and Electrification

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The recent report from the UN Intergovernmental Panel on Climate Change has increased the urgency on decarbonization. With many state and local governments setting limits on fossil fuels and carbon emissions for commercial buildings, the adoption of cleaner energy sources in the coming years will be necessary. Heat pumps, which provide an electric source of heat without the need for fossil fuels, and heat recovery technology, utilizing heat that is rejected during the cooling process, offer a comprehensive approach to decarbonization through electrification.

Heat Pumps

Heat pumps, which use electricity to move heat and boost temperatures, as opposed to transforming energy through the burning of fossil fuels, provide a clean and efficient source of heat. Traditionally, air-to-air heat pumps have been the most common, but with the widespread adoption of electric heating in commercial buildings, hotels, hospitals and industry, air-to-water and water-to-water heat pumps are gaining momentum globally as a long-term integrated approach with a lot of potential due to their increased efficiency and ability to operate at lower temperatures. Water-to-water heat pumps, which absorb heat in the evaporator in a waterside or hydronic system and then reject the heat through the condenser on the other side, can provide a sustainable heating source by allowing the building to recover rejected heat and reuse it, thereby saving energy and heating costs, while also reducing carbon emissions.

Heat Recovery

Heat recovery technology allows buildings to use rejected heat from cooling systems. Data centers, for example, have significant cooling needs due to the heat generated by the IT equipment. By recovering and utilizing the heat rejected during the cooling process, optimally with critical facility cooling systems that operate at very high cooling temperatures, the data center operator can reap measurable cost savings due to increased energy efficiency. The system gains 20 to 40% higher efficiency because of that higher temperature recovered heat. This means lower heat cost, providing a quicker payback vs the fossil fuel-based systems they are replacing.

For effective heat recovery, energy storage is critical. Obtaining 100% of heat through rejected cooling requires a perfect match between heating and cooling loads, which is unlikely for individual buildings, even in the most optimal conditions. To achieve a balance, building operators need to integrate storage – either cold, hot, or both, and potentially electricity storage as well – to reap the benefits of heat recovery technology. Another option is to increase the system scale, integrating multiple buildings and loads on a district scale, providing more load balance, built-in storage and additional options.

The Challenges of Electrification

While newly constructed buildings usually feature the latest in sustainable energy technologies, retrofitting older buildings with energy-efficient systems is a challenge. Boilers typically last for many years and building owners are often hesitant to replace systems that still operating at peak performance. Dual fuel systems, or hybrid systems, which use heat recovery chillers in combination with a boiler, are an innovative approach to reducing carbon emissions. The system can use the existing boiler with a flue gas scrubber, which provides cooling and removes contaminants from the atmosphere, to recover heat through a water-to-water heat pump, pre-heating the boiler feedwater and partially electrifying the heating system.

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