Heat pumps for water heating — interesting solutions with useful by-products

When it comes to beer cellar cooling, not to mention wine and produce storage, the hotel and catering sector has much to gain from heat recovery systems. Heat pumps will provide localised cooling in commercial kitchens and also offer waste heat recovery from plant boiler rooms creating free hot water.

Favourably comparing with conventional cooling where domestic hot water usage exceeds 500 litres per day, pay back from initial investment in complete heat recovery packages can be less than one year.

Owners at the Hundred House Hotel in Norton, Shropshire, were delighted when the first of two Calorex cellar cooling heat pumps had already paid for itself within months of installation while the payback period of the second was about 18 months.

A Calorex AW450SC in the wine cellar is directly linked into the hotel’s 1300 litre hot water storage tanks. This produces some 135 litres of hot water (10-50ºC) per hour. Electric immersion heaters top up the temperature for the kitchen and at times of peak demand, an oil-fired boiler may be used.

Although the wine cellar was cooled to 10ºC, the beer cellar next to it remained a little warm. A second AW450SC heat pump was installed that will allow the wine cellar temperature to be maintained and keep the beer cellar at a constant 13ºC. In addition, the system produces 270 litres of effectively ‘free?hot water per hour. Hot water use is sufficient to ensure operation of the coolers when needed.

The two units combined produce 12.6kW of heat to water and 8.8kW of cooling to the air for an effective COP of 3.15:1 per machine. This means that for every 1kW of electricity supplied to the machines, 3.15kW of water heating is available.

Social Housing

A 32-flat site in Paisley is a joint development programme between the Scottish and Danish Housing Authorities.

In the roof space of the building, a Calorex air to water heat pump converts air from the common kitchen and bathroom extract system to pre-heat the domestic hot water system. The heat pump is aided in this task by a vertical mounted solar collector.

All the flats in the building use a common extract system that will feed a supply of room temperature air to the heat pump at around 21ºC.

This air stream feeds into the heat pump, where the energy is recovered to provide pre-heated domestic water in the 35-45ºC temperature range.

The heat pump and subsidiary solar panels between them generate 80,000 kWhrs per annum of low cost energy.

Calorex  Tel: 01621 856611 or www.calorex.com