60% of the Danish population live in houses heated by district heating supplied by 400 district heating companies. Their member organisation – the Danish District Heating Association (DDHA) inaugurated new premises in 2006 including a Munters DesiCool system. The system was chosen as the DDHA wanted to utilise district heating as an energy source and emphasising their environmentally sustainable profile.
The DesiCool system creates a comfortable climate in the 2,200m2 building and during the winter benefits from its heat recovery principle. The total energy cost (electricity, water, district heating) for the first year amounted to only €4,500 for the 2,200 m2 building.
In 2008 the premises were enlarged by 1,000m2 and another DesiCool system was installed. The satisfied DHDA frequently brings visitors to view the system to emphasise utilisation of district heating for other purposes than just heating, eg. for cooling with a DesiCool system.
The environmental advantages are evident as the district heating is created from powerplants processing waste. As cooling would traditionally be produced in compressor driven systems, powered by electricity from gas or coal-fired powerplants, the green advantages of DesiCool are clear.
DesiCool can be powered by hot water at a temp at 55-60°C. Munters DesiCool uses nature’s method for humidifying and cooling air within their air conditioning technology in the form of desiccant cooling, A solution even more effective as it is converts surplus heat. Waste heat is converted into cooled and dehumidified air which is then distributed into buildings for better process results and people’s comfort.
Munters DesiCool air conditioning system uses this cooling principle to convert surplus heat at the DDHA district heating, into productive cooling within one unit, which contains neither a compressor, cooling surfaces or condensers.
In winter, the system provides an extra bonus as a heat recovery unit. Electricity consumption for DesiCool is 15% less than that for a compressor system. Coupled with the energy savings for heating the air in winter this results in 20% lower running costs for DesiCool depending on electricity and heating costs. With the maintenance reduction for cooling equipment the running cost savings are typically 40%. The result is normally a reduction in electricity consumption of 20% compared with cooling using compressors, and a heat recovery efficiency of 90% in winter.
DesiCool produces the best indoor climate in a building throughout the year because the system has no mixing of fresh air and exhaust air. It is always 100% fresh air from DesiCool. DesiCool processes the air by dehumidifying the air, then cooling it in a thermal wheel and finally cooling it further using an evaporative cooler. The system uses heat as the primary energy source for the cooling process – not electricity.
The desiccant section contains a rotating Munters desiccant wheel and reactivation coil. The indirect evaporative cooling component cools the exhaust air from the premises so that one can indirectly, via the rotating heat exchanger, cool the warm yet dry air that is generated after drying. The evaporative cooler in the intake air lowers the temperature of the cool yet dry air from the rotating aluminium heat exchanger before it is fed into the building.
To run the desiccant cooling process, the desiccant rotor has been specially developed to use water temperatures as low as 60-70°C for the reactivation coil, which provides the opportunity for using surplus heat from e.g. water cooled air compressors. More surplus heating means more savings in energy costs.
In the DesiCool process, using an outdoor design condition in summer, the ratio between supplied heat power and the supplied cooling effect is a factor of 2. For 20°C increase in temperature in the exhaust air through the reactivation coil, a 10°C temperature reduction in the air supplied is achieved. At lower exterior temperatures, the requirement heat power is reduced and completely ceases at an exterior temperature of 20°C. The cooling effect is generated by a combination of indirect and direct evaporative cooling.
The heat recovery in winter means under normal conditions - i.e. not below -16°C - the unit does not require extra energy to heat the supply air. Traditional air conditioning units with heat recovery use rotating aluminium heat exchangers for heat recovery. In the Munters system, the motor speed of the desiccant wheel is changed so the desiccant rotor becomes an enthalpy exchanger that transfers not only sensible heat but also moisture from the exhaust air. In tandem with the rotating heat exchanger this provides a temperature efficiency of 90% and a humidity efficiency of 75%.
The evaporative cooler works through water being added to Munters corrugated media. The heat required for evaporation is taken from the air flowing between the “corrugated” laminate. This way, the air is cooled and humidified at the same time. For each gram of water evaporated per kg of air, a temperature reduction of 2.5°C is achieved.
Munters DesiCool system
* Is environmentally friendly utilising no refrigerants
* Gives Energy savings
* Uses waste heat as an energy source
* Is easy to maintain
* Gives low running costs