Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.
Combined heat and power (CHP) production gains more
and more attention. Offices and public buildings often have a
large thermal power demand in combination with a fairly large
electrical power demand. On the other hand they are seldom
occupied by night and in weekends, reducing the actual
operational time of the heating system. This in turn brings
down the financial benefits of investing in CHP. A second
problem is that electrical and thermal demands are often shifted
in time. The running time of the engine is again limited this
way, as it is often not allowed to deliver electricity to the power
grid. A possible solution is using heat storage. This way the
CHP-engine can run when the electricity demand is high. In the
paper a simulation model of CHP with gas engine and heat
storage by means of a hot water vessel is developed. The model
is validated through experiments on an engine and a vessel.
This model is used to analyze the design, control and
performance of cogeneration plants. It is shown that storage is
marginal beneficial and the design has to be done with great
care.