NH3 heating & cooling at UK dairy slashes utility bills - Interview with R. Unsworth, GEA Refrigeration UK

By Alexandra Maratou, Sep 13, 2012, 10:24 6 minute reading

Incorporating ammonia reciprocating compressors, the energy-efficient heat pump solution for Robert Wiseman Dairies in Manchester recently won GEA Refrigeration UK Limited an Innovation Prize presented by trade magazine Food Processing. ammonia21.com talked to Robert Unsworth, Director of Sales & Development for CSO UK at GEA Refrigeration UK Ltd about this plant concept for simultaneous and energy-efficient provision of refrigeration and heat that has slashed the dairy’s gas bill by 5

ammonia21.com: GEA has successfully installed a two-stage ammonia heat pump which acts as a ‘bolt-on’ to the ammonia refrigeration system in a dairy business in Manchester, UK. What convinced the customer to invest in ammonia technology?

Robert Unsworth: Robert Wiseman Dairies have a national policy for removing man-made refrigerants over the next 20 years. So there was a project to look at removing three R22 chillers on the site but it had to be driven by return on capital on investment. Originally the project went out to tender via a consultant just as a traditional replacement of their refrigeration system.

The problem with it, as opposed to changing the refrigerant from R22 to a drop-in, was that the capital expenditure had a payback of 10-11 years. So it was not financially a viable project. Then I dreamt up the heat pump idea as basically a dairy takes milk in at cold temperatures, it heats it up to somewhere around 74°C degrees (depending on product) and then the refrigeration plant has to cool it back down again. A boiler provides the final stage of heating and the refrigeration plant provides the final stage of cooling (the heat put in by the boiler is removed later by the refrigeration plant, the only difference being the temperatures).

It is a perfect application for a heat pump. We take the energy that is typically thrown out in the ambient air through the condenser, and we put it back in to the system as hot water. And now they pasteurise milk with the waste heat from the refrigeration plant. You are merely moving the energy around rather than burning lots of gas.

ammonia21.com: What efficiencies have been achieved with the two-stage ammonia heat pump?

R. Unsworth: If you compare with what a typical dairy does at the moment, they burn gas through a boiler to generate steam that is used to heat water. The COP of gas boiler is around 80%, so for every 1kW of heat they have to burn 1.25 kW of gas and generate a lot of CO2 emissions doing so.

The refrigeration plant has a heating COPH of over 5 when we run the heat pump, so you get 5kW of heat for using 1kW of electricity. An additional benefit is that when you run the heat pump you are not consuming water or chemicals at the condenser stage. Also we managed to lower the condensing pressure of the main system, which makes the main refrigeration plant run more efficiently as well. So there are multiple aspects of savings with regards to the system not just with regards to saving gas.

What the end user has seen as net total savings is a reduction in gas usage of 52%, through entirely eliminating the need for burning gas for the pasteurisation process. Compared to running the previous R22 refrigeration plant, and although they are generating heat with a little bit more electricity, they have seen a net reduction of 20% on their electricity bill and their water bill reduced by 50%. We are about to add the site’s cleaning-in-place (CIP) and sterilization demand onto the heat pump also to maximize the operation of the heat pump and theoretically this should then remove the need for the boiler at all.

ammonia21.com: What is the advantage of the ammonia-based heat pump for this project compared to other heat pump solutions?

R. Unsworth: We could merely add a compression stage in practical purposes, in parallel with the condensers without the use of heat exchangers. Ammonia is an ideal refrigerant for providing both heating and cooling. Ammonia heat pumps have been around for many years. The difference here is that we are using multi-stage reciprocating compressors. Traditionally and even now on the market you buy an ammonia heat pump that uses screw compressors in this operation area. The problem here with these temperatures is that a screw compressor is less efficient than the reciprocating compressor and that you also have to dissipate some heat. One of the problems with the dairy is that the returning water is very hot – it might be 75-79°C - and one cannot use that for cooling the oil on the screw compressor, so the heat generated by the compression of the screw solution is thrown away (unless it can be used for some low grade application) and even so the screw is less efficient in this application.

With the reciprocating compressor, all the energy stays in the system and can be 100% recovered. So when we look at the dairy, the heat removed from the milk, the heat driving the refrigeration piston compressor, and the energy driving the heat pump is all recovered 100%, other than that passing to ambient via insulation, the pipes, motors etc.

ammonia21.com: What did you learn from this project, what challenges were encountered?

R. Unsworth: There have been some challenges, as this has been a bit of an R&D project. We had some problems with compressor bearing failure, but we have already solved these. And some challenges were simple things where suppliers of equipment had never operated in these conditions and therefore some components had a much shorter life expectancy than usual. Even reactions on refrigerant and oil which had been fully tested in our R&D facilities with no effect, were different in practice and needed consideration when the plant ran under real life conditions. Again through a step-by-step process with the client we have designed these flaws/components out of the system. Now it runs 24/7and actually quite reliably.

ammonia21.com: Where do you see greatest use of ammonia heat pumps in the future?

R. Unsworth: We have installed ammonia-based heat pumps for the poultry process industry, which requires a lot of hot water for removing feathers. We have installed 65°C hot water systems for bakeries for proving the bread and also cleaning and these systems have COPH’s in double figures compared to 0.8 for a boiler. We have installed heat pumps above a roof void of a large distribution store where they would normally install gas heaters to keep the temperature above the cold box warm so that you do not get condensation forming in the winter or frozen fire retardation systems . We have incorporated heat pumps through an air-handling unit to provide free heat in essence to heat the roof void of large distribution stores. We have also installed heat pumps for generating hot water for blanching vegetables before cooling or freezing them and drying potato chips before a fryer. All of this heat being recovered rather than discarded to outdoors. There are many applications. 

Contact information 

If you would like to contact GEA Refrigeration Technologies for any enquiries, you may send a request to Winfried Recker directly:


By Alexandra Maratou

Sep 13, 2012, 10:24

Related stories

Sign up to our Newsletter

Fill in the details below