J. Paavilainen* and C. Bales

Solar Energy Research Center SERC, Hogskolan Dalarna, 78188 Borlange, Sweden
Corresponding Author, jip@du. se

Abstract

A feasibility study for combining solar thermal plants with small scale 0.5-2 MWth mobile district heating plants under north European conditions was done. The study was done from a heat service company point of view, trying to come up with generally applicable scenarios rather than case studies. It was found that if the saved fuel is mainly pellets, without subsidies it is difficult to find economically feasible payback periods within the plants estimated lifetime, even with moderate pellet price increases. With oil as saved fuel the feasible payback periods range between 10-20 years with an estimated 5% annual oil price increase. The costs of moving the solar plant to another locations were also considered. A rough estimation of these costs resulted in a prolonged payback period of 3-6 years, which is considered too long regarding the general plant payback periods.

Keywords: district heating, feasibility, solar thermal, pellets

1. Introduction

Selling heat is a business concept (heat service company) for which the market has grown rapidly in the Finland and Sweden during the last decade in the scale of 0.5-2 MWth peak power district heating (DH) plants. In this concept the heat service company sells heat to customers, so that they own and operate the heat production plant and the customer gets only an invoice for used heating energy, as opposed to the heat consumer traditionally owning the heating plant in this scale. With probably the recent development in energy prices as a reason, the trend is such that customers also more often want relatively short term (5-10 years) heat delivery contracts, which gives them a chance to negotiate new contract terms or switch to another heat provider if the offered energy price is not satisfactory. Under these conditions the heating plant should be “mobile” so that it can be moved to another location without too high costs. A feasibility study to find out general boundary conditions for the economic feasibility of combining solar thermal plants with small scale DH networks in the above mentioned concept in Finland and Sweden is presented.