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Climate Change Case Study: Mahana Blue

Taking a punt on innovative energy-saving products has had great rewards for Auckland company Danfoss (New Zealand) Limited. The company develops and promotes, among other products, the commercial water heating system Mahana Blue which has helped farmers and business owners enjoy massive savings on their energy bills.

Although there have been other attempts to develop similar technology, Mahana Blue has revolutionised the way water is heated by utilising a new method to successfully harness waste heat from refrigeration systems and re-use it to produce hot water. The system is particularly effective in dairy sheds because of the high volume of hot water needed for cleaning and sterilising, and the amount of waste energy produced from keeping milk cold in refrigerators.

The unique concept of Mahana Blue was patented nine years ago by Peter Thompson, who knew that the technology behind the product worked, but could not find anyone willing to apply it in the field. Initially, Thompson thought Mahana Blue could be used to pasteurise milk on-site at farms. Many companies disagreed, but Danfoss could see the potential in the water heating benefits of the product and agreed to build a working prototype on Peter's behalf.

Danfoss Technical Manager George Hale explains the rigorous testing process for Mahana Blue. "We made the prototype and found it to be very effective, so we built a working model. After that, we installed a field trial version on a dairy farm at Waiuku and from there began on-site testing. We tested it thoroughly because we really wanted to make sure that the product did what we said it could do."

The test results concluded that Mahana Blue saves between 62 and 65 per cent of the energy required to heat enough water for a milking shed.

There are approximately 200 Mahana Blue systems operating in New Zealand and Danfoss's aim "is to assess each system individually, to see if we give people what we say we're giving them. We tell people they will have a two-year payback on their investment so we need to know if that's accurate," says George.

The system is also proving popular in places such as supermarkets and breweries. These types of businesses produce a significant amount of heat through refrigeration and also require a lot of hot water for cleaning and hygiene reasons.

The advantage is that unlike normal hot water cylinders, which can take hours to heat, Mahana Blue is able to heat the water closer to the time it is required. Large supermarkets can use up to 8000 litres of hot water daily and in some cases with Mahana Blue they can see a four-month payback on the product.

Mahana Blue is revolutionising the way wasted energy is treated in New Zealand. For farmers, the implications are huge. "There are 15,000 dairy farms in New Zealand with an average water heating electricity usage of 35 to 40 kilowatt-hours per day," says George. "If they all saved 60 per cent of that usage, the country would have an extra 360 megawatt-hours of electricity to use."

Figures from the Ministry for the Environment's Climate Change Office show that global energy use has increased nearly 70 per cent since 1971 and is likely to rise at more than 2 per cent annually for the next 15 years. Most urban greenhouse gas emissions are from energy use.

Around a third of New Zealand's electricity is generated by burning fossil fuels such as coal and gas which emit carbon dioxide into the atmosphere (the other two thirds are generated from renewable sources such as hydro). To reduce these emissions and save money on power bills, businesses need to think about conserving energy (using less) and being more energy efficient (using energy wisely).

Last updated: 14 April 2008