Epsilon Archive for Student Projects

Abstract

The purpose of this thesis was to make an energy survey and quantify energy flows of
individual unit operations associated with the biogas production in Uppsala Vatten och Avfall
AB:s biogas plant, located at Kungsängens gård. Moreover, large consumers of energy would
be identified and analyzed. The objective of this energy survey was to obtain a detailed
understanding of the energy use in the biogas production.

The energy survey was divided into two parts: electricity and heat. Each part was treated
separately and with somewhat different approach. To estimate the electricity usage during the
projcet the rated power of each selected unit operation was noted and multplied with the
measured time of usage. By doing that the total amount of energy consumed is obtained.

During the project a total amount of 152 kWh/ton electricity was used. The 12 largest
electricity consumers had a combined usage of 106 kWh/ton, corrresponding to 70 %.

The heat survey was subdivided into hot water and steam. Hot water is used to keep the
biogas digesters and facilities warm. Steam is exclusively used in the heat pretreatment.

Thermal energy consumption was as following:

· Keeping the biogas digester warm consumed close to 20 % of the total heating
demand, corresponding to 40,8 kWh/ton.

· Heat pretreatment accounted for 62 % of the total heating demand, corresponding to
129 kWh/ton.

· Heating demand for other staff facilities accounted for 18 % of the total heating
demand, corresponding to 37,7 kWh/ton.