The idea of decentralised, heat-led thermal power plants is at the forefront of ESS installations. In the compact units, on the one hand, electricity is generated for internal needs and, on the other, the incidental exhaust heat of the engine is used largely without loss for heating and is not discharged into the environment. Electricity which is not required is fed into the public network.
Thermal plants are extremely efficient. While conventional power plants achieve overall efficiency of barely 40%, for thermal plants, this figure is over 90%. Through the deployment of a thermal plant, primary energy consumption is reduced by well over 30% and CO2 emissions by up to one third. A thermal plant can be operated with biogas or with biomethane (raw biogas which is processed and fed into the natural gas network) in a particularly environmentally friendly way, since it works on a CO2-neutral basis. Through it, agricultural enterprises can become independent of fossil fuels such as natural gas, since the biogas can be generated from raw materials which grow in the region. The „Vitobloc“ thermal plants produced by ESS are available with electricity generating capacities of 20 to 401 kW and with heat generating capacities of 39 to 549 kW.
At AGRITECHNICA in Autumn 2011, ESS will offer a biogas-fuelled thermal plant in the 75 kW capacity class, which is extremely attractive for many farmers. The new installation is specially designed for deployment close to farms and for enhanced fermentation of liquid manure. The Renewable Energies Law (EEG) 2012 codifies the promotion of small biogas installations fuelled by liquid manure, with capacities of up to 75 kW. The remuneration for feeding in electricity through this installation will rise in 2012 to an attractive 25 cents/kWh.
ESS delivers each individual installation in turnkey condition. The customer can also assemble a tailor-made service package, ranging from commissioning to training to complete operation. ESS staff are always happy to help when it comes to commissioning, maintenance, service, repair work or overhauling of engines. Various maintenance contracts provide a balanced price to performance relationship and risk-free all-round service. All central power plants can be monitored and controlled remotely by the ESS service. Within Germany, ESS maintains a factory service with some 30 support points. Outside it, the service is carried out by reliable partner firms.
ESS thermal plants deploy gas engines of leading manufacturers, such as MAN or Toyota. The engines should be operated exclusively with a gas engine oil with special additives, approved by the OEM. According to the type of engine and gas, the overall or volume ranges from 35 to 220 litres. For engines operated with natural gas, oil is predominantly changed at fixed intervals. In biogas installations and in turbo systems with heavy loads, ESS recommends changing the engine oil as a function of its condition. The optimal time is defined by OELCHECK with analyses of lubricants.
Gas engines represent a genuine challenge for their engine oils. Ultimately, the facilities operate on a continuous basis, at high process temperatures and frequently under full load. For operation with biogases, individual and highly variable qualities of gas are added. The composition of biogas depends on the respective fermented organic material. In addition, it is hardly ever pure. In addition to 50- 75% methane, biogas contains nitrogen, carbon dioxide, water and oxygen. Very frequently, mainly for the fermentation of liquid manure, hydrogen sulphide is also present and can form aggressive hydrogen sulphide (H2S). This can generate corrosive wear and tear on pistons, cylinders and in the valve train. A further risk for gas engines and a major challenge for engine oil is posed by sulphuric acid, generated in the combustion process for the gas. The gas engine oil must have a high alkaline performance reserve in order to neutralize these acid components, as well as to neutralise the hydrogen sulphide. The acid-buffering additives must be ash-poor and cannot be added in excessively high doses, since otherwise, the performance of the catalyst will be impaired. If it does not succeed in striking a balance between few additives and good neutralisation capacity, the oil can no longer lubricate the engine reliably and protect against wear and tear, corrosion and deposits