“Solar thermal systems are still too expensive, meaning they can’t compete with the comparatively low-priced heat from biomass boilers,” said Aurimas Lisauskas, Research Associate at LEI and author of the district heating study conducted during EU project SDHplus (2012-2015). As part of SDHplus activities, Danish-based consultancy PlanEnergi created a feasibility study on an SDH system in a Lithuanian village called Raseiniai. The first scenario was based on a stable biomass price over 30 years of operation, which resulted in payback periods of 24 to 25 years. The payback period itself was calculated using a simple formula to divide the saving from operation by the investment.
The assumptions were:
- Solar radiation in Lithuania is between 850 and 1,050 kWh/m²;
- Storage volume is at 0.25 m³ per m² of solar collectors;
- Collector field prices range from 300 EUR/m² for a 2,000 m² field to as low as 200 EUR/m² for a field of 27,400 m²;
- The specific solar yield is 475 kWh per m²;
- The real interest rate, i.e., nominal interest rate minus inflation, is 3 % over 30 years;
- Solar heat replaces most of the heat from biomass boilers;
- Capital costs are calculated over 30 years.
In a second scenario, biomass prices were expected to increase by 1 % annually, as assumed by the Danish Energy Agency, and the solar investment was reduced by 10 %. The results are shown in the chart below. The simple method decreases the payback period to between 19 and 22 years, and solar fields above 15,000 m² offer lower heat prices than the reference case, which relies solely on a biomass boiler for heat production. Optimum solar collector area is at around 22,500 m², but other sizes could also be feasible.
Average annual heat prices, calculated as a combination of heat produced by solar and biomass and at a real interest rate of 3 % over 30 years. The reference heat price is 25.1 €/MWh, provided that heat is produced by a biomass boiler only.
Source: PlanEnergi / Solar Thermal World.org