Efficient use of arable land for energy: Comparison of cropping natural fibre plants and energy plants

R. Pecenka*, H.-J. Gusovius, J. Budde and T. Hoffmann

Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB), Max-Eyth-Allee 100, DE 14469 Potsdam, Germany
*Correspondence: rpecenka@atb-potsdam.de

Abstract:

With focus on renewable energy from agriculture governments can either support the growing production of energy crops or it can invest in technology or measures to reduce the energy consumption. But what is more efficient with regard to the use of the limited resource arable land: to insulate a building with fibre material grown on arable land to reduce the heating demand or to use such land for growing energy plants for the sustainable energy supply of a building? To answer this question, a long term balance calculation under consideration of numerous framework parameters is necessary.
Based on traditional fibre plants like hemp, flax, and woody fibre crops (e.g. poplar), these agricultural plants and their processing to insulation material were examined. Based on available data for the typical building structure of detached and semi-detached houses in Germany, models of buildings were developed and the accessible potentials for heating energy savings by using suitable insulation measures with natural fibre materials were determined. As a comparable system for the supply of renewable energy, bio-methane from silage maize was chosen, since it can be used efficiently in conventional gas boilers for heat generation. The different levels of consideration allow the following interpretations of results: in a balance calculation period of 30 years, the required acreage for heating supply with methane can be reduced by approx. 20%, when at the beginning of the use period fibre plants for the insulation of the houses are grown on the arable acreage. Contrariwise, to compensate only the existing loss in heating energy due to inadequate insulation of older detached and semi-detached houses (build prior to 1979) an annual acreage of approx. 3 million ha silage maize for bio-methane would be required in Germany. Therefore, from the land use perspective the production of biogas plants in agriculture for heating should be accompanied by the production of fibre plants for a reasonable improvement of the heat insulation of houses.

Key words:

bioenergy, biogas, fibre, heat insulation, heating., natural fibre plants

Case study of increasing photovoltaic energy solar fraction in a conventional office building in northern latitudes

P. Pikk* and A. Annuk

Department of Energy Engineering, Institute of Technology, Estonian University of Life Sciences, Kreutzwaldi 56, EE51014, Tartu, Estonia; *Correspondence: priit.pikk@emu.ee

Abstract:

Current trends in planning office buildings are moving towards reducing primary energy consumption for heating, hot water heating and cooling. Availability of the solar energy resource and the low temperatures in northern latitudes from early spring until autumn provide the possibility to use photovoltaic (PV) energy for heating, cooling and other energy needs. This article calculates the heating, cooling, hot water and electricity demand of an office building with a glass facade of 65% of the total wall area. The calculated annual total energy consumption is 120 kWh m-2. To reduce the heat and electricity consumption from district heating and the power network, PV modules are integrated into the roof and facade and the solar fractions of the PV energy of the four energy loads (heating, cooling, hot water, and electricity) are found. Optimization of the PV module tilt angles on the facade and roof results in the maximum solar fraction for cooling, heating, preparing hot water, and electricity consumption, 98.4%, 32.1%, 71.7%, and 51.6% respectively. For total load, the calculated maximum solar fraction is 49.8%.

Key words: