The introduction of the Renewable Heat Incentive (RHI) at the end of 2011 has generated a massive growth in the UK biomass market.
In addition to the financial benefits for biomass fueled boilers, the RHI incorporates even more attractive incentives for biomass Combined Heat & Power (CHP) plants. However, there are very few proven biomass CHP systems on the market.
NewEnCo was delighted to add the Q-PowerGen Biomass CHP System, manufactured by Qalovis in Germany, to its product portfolio in 2015. This system combines a biomass gasifier and the technically innovative FleXgen Stirling engine CHP for the efficient generation of electricity and heat.
The key specifications and advantages of the Q-PowerGen Biomass CHP System are summarised below:
Electrical Power Output: 36 kW, min 20kW turn down
Thermal Power Output 120 kW, min 85kW turn down
Biomass fuel consumption: depending on product quality < 52 kg / hr
Fuel options: Natural wood as chips, wood pellets, Biomass Pellets with N <1 wt -%, CI uS <0.01 wt -%; general: water content <20 wt -%; Pellet diameter and length at least 6 mm
Exhaust Gas Flow: 1500 m³/h at 120 DegC
Space requirement: 6.5m square (including maintenance access)
Waste ash can be composted as it is free of environmentally hazardous PAHs (polycyclic aromatic hydrocarbons).
The technical datasheet for the system is available for download below:
The innovative use of the Stirling engine is what really makes the Qalovis system different from anything else currently on the market. The basic construction already differentiates the Qalovis Q-PowerGen biomass CHP from other thermochemical wood gasification systems. In the Qalovis plants, other biofuels can be burned, and not just the wood energy source usually used. Whereas traditional wood gasifiers focus on the processing of the “wood gas“ formed in combustion engines, the integration of the Stirling engine opens up completely different possibilities.
In the Q-PowerGen system, the generator gas formed in the gasifier (main components nitrogen, carbon dioxide, carbon monoxide, hydrogen and steam), is no longer cooled and filtered in complex processes. Only the cooling of the generator gas leads to the formation of tar in other systems. As long as the gas is not cooled to below 350° C, no tar is formed. So what is separated as tar in other “wood gas“ plants remains here in the generator gas as an energy-supplying component! No catalytic converter is required. Because the generator gas is added to the burner while it is still hot, substantial energy components remain in the gas. The gas ignited in the burner can then be burned out in a separately optimised combustion chamber.
Enclosed in the FleXgen Stirling engine is a pure hydrogen gas - also known as working gas. If the gas is heated, it expands - if it cools, it contracts. The expansion and cooling of the gas is converted into a piston movement. On the Stirling engine, the heating and cooling of the pure working gas takes place - in contrast to with the combustion engine - through heat transportation through a wall: here heat exchange surfaces are required. This form of thermal transport is always “slower“ than the fast exchange of gas in the cylinder of a combustion engine. For this reason, Stirling engines behave very differently to the standard combustion engines. In the FleXgen Stirling engine, heat exchange surfaces for heating and cooling, cylinders and pistons and a solid matter heat accumulator called a regenerator are interconnected so that the hot side of a cylinder is connected via the heater, the solid matter heat accumulator and the cooler with the cold side of the neighbouring cylinder. The hot and cold mediums are separated in the cylinder via the piston. In total, four cylinders are interconnected in this way. For the engine, it is irrelevant where it derives its driving heat. The heat-supplying medium is kept separate from the enclosed working gas - the engine interior remains protected against contamination. The FleXgen can thus also generate mechanical work from hot combustion exhaust gases. In this form, the FleXgen is unique, and represents a technological breakthrough.
Wood, as a widely-used biofuel, is still substantially less expensive than the conventional energy source gas and oil. It is however to be expected that the wood price will continue to rise over the next years. The fuel costs are a decisive economic factor, in particular for energy-intensive businesses. The question is, therefore: What inexpensive fuel alternatives exist for biomass CHPs? One focus Qalovis development work is the widening of the fuel spectrum for our Q-PowerGen plants. Therefore, wood chips from different sources (sawmill chips, forest wood chips, chips from landscape maintenance/hedge cuttings) can already be used. Pellets from other materials such as cereal straw, straw from other cultivated plants, by-products from biogas plants and even by-products from livestock farms are being tested as potential fuels. We are also investigating imported bioenergy sources such as palm seed husks for their suitability.