Food Processing magazine spoke to Robert Unsworth, head of sales, Utilities at GEA UK, about the potential energy saving benefits that modern heat pumps can offer in the food processing sector.
Q. Food Processing readers should already be aware of many of the energy efficiency benefits of heat pumps, but what benefits can an ammonia-based heat pumps offer over the many other refrigerant choices available?
Ammonia is a more efficient refrigerant than any of the synthetic gasses. With an enthalpy (how much heat per kg it absorbs) several times greater than any synthetic gas, you need less ammonia to provide the same amount of cooling/heating, assuming that the system is designed properly. Unlike other gasses, it has 0 GWP and Ozone depletion figures. Unlike synthetic gasses, it smells when it leaks in very small quantities so leaks can be quickly and safely dealt with. However, ammonia leaks are rare because of the legally required practices for its use and the materials and practices used in the systems which contain it. While ammonia is mildly flammable, you would need a lot of it and it is non-propagating – unlike the new synthetic gasses entering the market. It also operates at relatively low pressures in heat pump applications when compared to other gasses. However, its main benefits are that it is efficient, environmentally-friendly, future-proof and you don’t need much of it. A heat pump with a capacity of 1,000kw would only have a charge of 40kg but would supply over 375m3 of +65°C water every day at a cost of approximately one-third that of a boiler, with half the C02 impact.
Q. Might the use of heat pumps pose any particular issues, or benefits, for the food sector?
As far as I can see there are no negatives! especially in the food sector. It puzzles me that ground and air source heat pump are growing at a rate of 40% year-on-year, yet these types of heat pump offer nowhere near the energy efficiencies possible in food sector applications.
If, for example, you were to apply a heat pump to absorb heat from the River Thames at a temperature of +2°C and then boost it up to +65°C, the heat taken out of the water is, in effect, doing nothing… we are merely cooling a few fish. So, if you took 1,000kw of heat it would cost 310kw of electricity to boost it up to +65°C, but we can recover both so we get a total of 1,320kw of heat, But in effect we have absorbed 1,000kw from the river.
A food factory is, basically, a large refrigerator. Heat enters the building via the walls and people, but also the product which may enter at ambient temperatures, get cooled (heat removed(kw)), heated up (heat added(kw)) and then finally cooled down or frozen again (heat removed (kw)).
The primary role of the refrigeration is to remove these kw’s of heat from the insulated factory, but the heat is then thrown away at about +30°C via the condenser on the roof. A heat pump would simply lift this wasted heat from +30°C to a useful +65°C (higher temperatures are achievable), using just 161kw of electricity to give you the 1,309kw of heat. Further, if you reuse heat, it means less fans are needed to run the condenser because there is less rejected heat, offering even greater potential energy savings.
There really is no bad side to employing heat pumps and all factories should really be looking at using the technology.
Q. So, you have demonstrated how heat pumps can offer an economical heating solution, but what can GEA bring to the party, to satisfy the needs of those looking for even greater energy efficiencies from their processes?
Where GEA can add value, in addition to its technology capabilities, with that the company holds vast amounts of process knowledge, with specialists in all areas. We combine this knowledge to create the best overall solution for a customer. For example, without a deep knowledge of the brewing process, a refrigeration plant which on paper looks set to deliver the right cooling capacity, will probably not operate efficiently under the dynamic nature of the load requirements of this sector. Likewise, if you want a system simply to cool an abattoir but do not consider product moisture loss, you might save money in capital outlay, but will spend much more watching all the moisture disappearing down the defrost drain.
Traditionally companies have only looked at the cooling aspect of a system. However, being able to reuse heat taken from a product via a heat pump means that it is important to work more closely with our food and dairy process colleagues to understand the heat recovery and reuse opportunities earlier in a project – maybe providing heat for cookers/dryers/fryers. This was the whole point of the ‘One GEA’ project – for our customers to see GEA as a partner who can provide a single source for solutions to a diverse range of applications. After all heat is heat, whether it is at -40 or +40°C, and GEA is really good at moving heat around.
Q: Can you give us some typical applications where GEA’s RedAstrum ammonia heat pump solution might really come into its own?
Anywhere in a factory where you are cooking, heating, making hot water, pasteurising, or blanching! I have yet to see a food process where there is not enough heat to reuse and supply to another process. To be honest the RedAstrum heat pump is just a chiller, which, instead of rejecting the heat into the outside air at +30°C, rejects it into water at +65°C (or hotter) and recovers it.
Typically the capital cost of this will be similar to a boiler so there is no excuse for a heat pump, combined with a refrigeration system, to not be considered in all new plants.
In existing plants, with a legacy boiler house and steam distribution system providing heating, the heat pump will need to pay for itself through reduced running costs. Currently, this is achievable in between two to five years, depending on size and amount of distribution required. This will, of course, be governed by the cost of fuel. GEA regularly see reductions greater than 60% in fuel use.
Heat pumps running on the back of refrigeration systems are definitely the future and they are here to stay.