VALTEC

Rural electrification with renewable energy equipment offers several advantages (and may be the only alternative) in rural areas where conventional electricity supply is constrained in developing contexts, or may lead to systems that are self-sufficient in energy terms in developed areas. VALTEC aimed to develop a small-scale downdraft gasifier up to the prototype phase, using the resulting synthesis gas (syngas) in an engine-generator to produce electricity in a range of 5 to 50 kWe.

Such systems are suitable for autonomous generation in both industrialised and developing countries, and allow traditional diesel generation to be replaced in hybrid configurations, or the syngas to be used in dual mode with diesel. The project therefore also included the research and development needed to adapt existing microgrids to the use of gasifiers. As this technology belonged almost exclusively to Indian and American manufacturers, the objective was to develop the group’s own technology, applicable to remote areas in Europe and in an international framework led by Catalan companies.

The main objective, a downdraft biomass gasifier prototype able to supply 10–15 kWe and to be connected to a microgrid for electricity distribution, comprised the following specific goals:

• Develop a pilot downdraft gasifier suitable for gasifying a biomass flow rate of 10–20 kg/h, mainly hardwoods with a grain size between 20 and 50 mm.
• Establish the design and operating conditions that minimise the content of tars and particles in the syngas and deal with the reactivity of the biomass ashes.
• Design, adapt and optimise the gas cleaning system in order to obtain a syngas suitable for combustion in the adapted engine.
• Assemble an engine-generator system downstream of the gasifier and gas cleaning structure, and tune the electricity production and control systems with the corresponding stability tests, including studies of the input and output transient stability of the power service.
• Tune an electricity generation microgrid, managing demand and production in mono-generation mode or in hybrid mode with solar photovoltaic systems.

As competitive advantages, the project aimed at developing its own tar-free technology while dealing with the challenge of biomass ash reactivity, advancing the state of the art of commercial downdraft biomass gasifiers and adopting dry gas cleaning, which leaves no aqueous effluent to be treated before disposal. A high degree of automation was also sought in order to lower operating costs, with the aim of reaching the level of the most advanced technologies then available at pre-commercial or commercial stage.