Optimal use of solar collectors for residential buildings

Solar radiation is an abundant free resource which may be used in the form of solar heated water. This is achieved in solar collectors which, unfortun ately, are expensive devices and, further, the warm water must be stored in accumulators-items which also cost money. This paper shows how we have opt imized the situation for a block-of-flats in Sweden. In order to find this point we have used the minimum life-cycle cost (LCC) concept as a criterion . The best solution is therefore found when that cost finds its lowest valu e. It is also examined under which conditions solar collectors are part of the optimal solution and further it is calculated what happens if this opti mal point is abandoned, i.e. how much will the LCC increase if other than o ptimal solutions arc chosen. LCC optimization for multi-family buildings al most always results in a heating system with low operating costs such as di strict heating or dual-fuel systems where a heat pump takes care of the bas e load and an oil boiler the peak. The installation cost must, however, be kept to a reasonable level. Expensive solar panel systems are therefore nor mally avoided if the lowest LCC shall be reached, at least for Swedish cond itions. This is so even if the solar system has a very low operating cost. For buildings where the only alternative energy source is electricity, sola r collectors seem to be on the rim of profitability, i.e. for an energy pri ce of about 0.6 SEK kWh(-1). Copyright (C) 2001 John Wiley & Sons, Ltd.