Making waste heat useful thanks to industrial heat pumps

At the first ever Energy for Sustainability Multidisciplinary Conference, GEA Refrigeration Technologies presented the paper “Optimising heat recovery by integrating industrial heat pumps with other energy systems” on the important role that industrial heat pumps can play in moving low-grade heat from one customer to another customer in the form of valuable high-grade heat.

The paper, by GEA Heating Application Manager Kenneth Hoffman, looks at the various options for waste heat recovery to optimise total system performance.

Flue gas heat recovery increases electricity production efficiencies to 100%

Much of the electricity produced today from fuel combustion is generated without recovering heat from flue gas. However, recovering the heat can increase the efficiencies of electricity production from between 40 or 50% to 100%, improving power plant economics.

Using direct heat exchange with hot water to recover heat from the burning of fuel with low moisture content such as gas, oil, and coal, allows over 90% of the heat to be recovered. With wet fuels such as biomass and waste, a wet scrubber system is also needed, as only 80% of heat recovery from the combustion process is possible by direct heating of water. The wet scrubber system has the added benefit of reducing toxic emissions from fuel combustion.

Combining heating and cooling needs through waste heat recovery heat pumps

In many processes, cooling and heating demands are individually covered without a full production layout of heating and cooling needs, leading to wasteful energy flows. For example the dairy industry demands both high temperature heating and cooling.

Rather than using cooling towers to cool wastewater from production processes, useful heat can be generated from the waste heat using a high efficiency ammonia heat pump. This type of waste heat recovery can result in good payback, with heating COP’s that range from 4 to more than 12.

In the UK, GEA Refrigeration installed an ammonia heat pump in a dairy facility to recover waste heat from the refrigeration plant at 24°C, and heat water for pasteurisation from 72°C to 82°C. The installation achieved a payback of 1.5 years and saves more than 1000 tons of CO₂ emissions a year.

Using ammonia heat pumps to increase solar heating efficiency

In order to optimise large scale solar heating systems, heat pumps can be used to precool water to the solar panels, thereby improving the efficiency of the panels, and boost the hot water supply temperature when there is not enough sunshine.

Background

The conference in Energy for Sustainability was organised with the aim of creating a forum where stakeholders, researchers, practitioners and students from different scientific domains could meet to discuss and share their experiences and proposals regarding approaches to tackle the need for a more sustainable world.

About GEA refrigeration Technologies

GEA Refrigeration Technologies is a leading global group in Industrial Refrigeration. They design, engineer, install, and maintain innovative key components and technological solutions for their customers for whom refrigeration is an essential part in their primary processes.

GEA Refrigeration Technologies, part of the internationally active GEA Group, is synonymous with industrial refrigeration technology. Since the end of the 19th century, it has been their business to cool processes and products, and to control the temperature of goods in transport. Their solutions are present in the food and beverage sector; petrochemical, chemical, and pharmaceutical industries; on fishing ships; in natural gas liquefaction; in infrastructure facilities; and in ice factories.