The domestic hot water was set to the standard value for the NOVEM reference house being 10.2 GJ/day (for all 4 houses). This was translated into a water volume of 134 litre/day to be heated from 15 to 65 oC. Five times a day one fifth of the daily water consumption was drawn off (7, 8, 13, 18 and 19 hour).

The heating of hot water is preferent to the space cooling of the house. So the storage of the solar system is first heated up to around 70 oC before cooling of the house takes place (or can even take place with a single effect system). The waste heat of the condenser/absorber is not being used to preheat the domestic hot water. This would make the system too complicated.

Sorption System

For cooling in summer the sorption system is driven by the solar system with temperatures below 100 oC. In winter the sorption system can be driven by the auxiliary heater at higher temperatures (the higher the generator temperature the higher the power of the sorption machine and the better the price/performance ratio). We presume a generator temperature of 150 oC in winter, however this will complicate the system design (i. e direct firing).

The sorption system is characterised by the heat transfer values of the evaporator, generator and condenser/absorber according to the zero order model. The following values were used as default:

• Evaporator heat transfer: 200 W/K

• Condenser/absorber heat transfer: 400 W/K

• Generator heat transfer: 200 W/K

This set of heat transfer values delivers 5.5 kW of condenser/absorber power at a generator temperature of 150 oC, a condenser/absorber temperature of 50 oC and an evaporator temperature of 10 oC. The generator power is in this case 3.6 kW and the evaporator power is 1.9 kW. So the cooling COP is 0.53 and the heating COP is 1.53. Of course these values depend strongly on the generator, condenser/absorber and evaporator temperatures, however the condenser/absorber power at these temperatures was used to characterize the system in the following figures. For example a condenser/absorber power of 2.75 kW represents a sorption system with 100 W/K evaporator heat transfer, 200 W/K condenser/absorber heat transfer and 100 W/K generator heat transfer.

Solar system

A typical selective flat plate collector with the following characteristics was used:

no = 0.797 [] Efficiency at zero temperature difference

U = 4.22 [W/m2K] Constant part of heat loss factor

Ut = 0.00504 [W/m2K2] Temperature dependent part of heat loss factor

The collector area was in most simulations 8 m2 while the sensible heat storage was kept at

300 litre. These are standard values for a solar combi system with standard flat plate

collectors in The Netherlands. With lower collector area the contribution to the space heating

becomes negligible. With these dimensions the heat surplus in summer is rather big,

because in summer 2 m2 of collector area would be sufficient for hot water.

In stead of standard flat plate collectors also high efficiency evacuated tube collectors (for example Sydney type) can be used. In that case around 30 to 40% smaller collector areas are possible with the same contribution to space heating, hot water and cooling.