A team of researchers led by Newcastle University has produced an all-in-one Biofuel Micro Trigeneration (BMT) prototype system fueled entirely by unprocessed plant oils that provides combined cooling, heating, and electrical power. This first-generation system is designed for use in homes, with the potential for up-scaling for larger commercial and industrial applications.

Claimed to be able to use many types of unrefined plant oils – including sunflower, rapeseed, jatropha, and croton – the BMT system is claimed to enable distributed heating, cooling, and electrical power. Using a diesel engine generator modified to produce power using renewable plant fuels, the BMT is coupled to a hybrid electrical energy storage unit and a data acquisition and control system to provide reliable electricity without the need for a mains connection.

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By using unrefined plant oils, waste products and energy used to convert the plant matter to oil are reduced. In this reductive vein, waste heat from the engine is recovered and used to supply heating and hot water, as well as being used to drive an ammonia/water diffusion type absorption refrigerator. Fuel efficiency optimization is also achieved by storing power at times of low electrical demand and ensures that the engine operates at high load for the shortest period possible by using an electronic regulator system.

"The challenge was to design a system that could simultaneously satisfy the more predictable needs for heating and hot water, as well as the wildly varying demand for electricity in a small dwelling," explains Professor Tony Roskilly, of Newcastle University. "Our solution was to incorporate advanced electrical storage into the system, both batteries and the latest supercapacitors, combined with innovative system control."

BMT systems are not new for large-scale factories and plants, but this system is the first to claim both efficiency for small premises and the use of unprocessed oils as fuel. By using an intelligently-controlled process that combines storage, waste heat recovery, and efficient cooling, the team claims to have produced a small-scale BMT able to cope with the daily fluctuating demand for electricity found in the average home.

Claimed to be ideal for applications in the developing world, the team also conducted studies into the ideal oils that could be used and – more importantly – were available in places where industrialized processes for refined oil were not in place. It was also important that the biofuel requirements would not impinge on the locals’ ability to grow food crops.

"We wanted to avoid running the tri-generation system using biodiesel or other highly-processed fuels from raw materials," says Professor Roskilly. "So instead, we developed a system for using the oils obtained from pressing crop seeds, like those from jatropha and croton. These crops can grow in harsh environments and on poor-quality land and so could be well-suited to providing fuel in developing countries, as cultivating them would not adversely affect food production. The potential demand for this technology in such countries is very large."

A domestic-scale BMT of the sort described by the Newcastle University team would apparently be able to supply around 6 kW to 9 kW of electricity, which is the equivalent power needed to run lights, a television set, a refrigerator/freezer, a kettle, a microwave oven, a vacuum cleaner, a washing machine, and a dishwasher if all were switched on at the same time.

Along with a follow-up study looking at the potential for the system to be used on small farms in the developing world for refrigerating and processing food crops as a way to reduce losses after harvesting, the team is currently examining the long-term performance of the system running on "raw" plant oils and is in talks with manufacturers with a view to commercializing the design.

The system was developed as part of a three-and-a-half-year project that received funding from the Engineering and Physical Sciences Research Council (EPSRC), through the Research Councils UK (RCUK) Energy Program. The team also included researchers from the University of Leeds, the University of Ulster, and three Chinese universities.

Source: Newcastle University