Hållbara uppvärmningsalternativ för Grinda Wärdshus
En studie om uppvärmning med pellets och flis
This report is a bachelor's thesis of two students from the Energy and Environment degree at KTH Stockholm. Grinda is an island situated Stockholm archipelago. Skärgårdsstiftelsen is landowners and manages the area. Grinda Wärdshus, a guest house located in the island, currently uses an oil-fired boiler as a heating system. The aim of this thesis is to investigate whether wood chips or pellets is, from a sustainability standpoint, a suitable heating method for the guest house. A literature review and a field study are carried out to create an information base. The current heating demand was calculated by adopting all heating produced by the oil boiler. The heating power demand was determined by comparison of bids, information from the owner of Grinda Wärdshus and guidelines from work of previous quotes. Different options for a new heating system are presented. By using quote and assumption models, proposals for investment costs and annual costs are created for different heating systems. A model for production of wood chips on the island is also calculated and evaluated.The wood chip options have higher investment cost in comparison with the corresponding pellet options. Cost Proposal for new heating system is evaluated with pay-back and net present value 15 years after the investment. The wood chips option has a faster pay-back and a better development of the capital value. Variations in fuel prices are taken into account to investigate the sensitivity of the models. Comparison of the annual carbon dioxide emissions shows that pellets causes lower emission than wood chips. The difference is about 300 kilograms. In comparison with the use of oil, pellets and wood chips would contribute to about 57 tons less carbon emissions. Further study needs to be done determine which of the alternatives, wood chips or pellets, is the most beneficial heating fuel option for Grinda Wärdshus. Both solutions are economically and environmentally beneficial. Wood chips are cheaper, but require more effort work for production and operation.