Open access publications in the SLU publication database

In order to decrease the climatic impact of carbon dioxide (CO2) emissions from burning fossil fuels a carbon dioxide tax on fuels that are not renewable has been introduced in Sweden. This means increased costs for greenhouse growers using natural gas or oil and a strong incentive to convert their heating systems from fossil to renewable fuels. Some Swedish greenhouse growers have already converted to renewable energy, but still a large number of growers use fossil fuels. Increased knowledge of how to decrease the energy use and the use of renewable energy are demanded by many growers. In the present project knowledge of renewable energy sources and technical design of heating plants using renewable energy for heating greenhouses are collected together with economic decision models. In the chapter "Energy systems for greenhouses" a review of the heat balance for a greenhouse and different ways of heating the greenhouse is provided. The renewable energy sources started to be used later years for heating Swedish greenhouses are primarily bark (cortex), wood chips, splint, pellets and biomass briquettes. Some firewood and straw are also used while only small amounts of biogas and peat are being used. Heat pumps are interesting for heating greenhouses in some cases and for generation of electric power e.g. solar panels, and in special cases also small scale hydro power can be of interest. For heating greenhouses solid biofuels (wood fuels) like wood chips and wood pellets etc. are in most cases the most interesting alternatives to fossil fuels. The heating value, i.e. the amount of energy released during the combustion, varies largely with the moisture content of the wood fuel and between different types of wood chips. In the chapter "The central heating plant and its components" systems for removal of particulates, heat storage in buffer tanks, and knowledge of how to operate wood-burning heaters are included, and in the chapter "Authority requirements, examinations and inspections" an overview of different requirements and regulations is provided. In the chapter "Economy and decision model" costs and investment calculations are discussed. When planning a new or when rebuilding an old heating plant, a good way is to first lower the power- and energy demand as much as possible by e.g. increased insulation and after that look at different alternatives for heating. This leads in far most cases to a significantly lower cost for the heating plant. 10