POWER GENERATION IN THE HILLS

Since the closure of Fluidyne's manufacturing facility in 1998, there has been little opportunity to use the small Pioneer Class gasifier and 6.25 kva generator set that I used for demonstration training and testing fuels. Late in 2005, it became necessary to pull this equipment out of storage and set it up temporarily for a demonstration and training programme. This was held at the end of January 2006 here in New Zealand as the first stage of implementing a new project to manufacture a gasifier in Australia designed for their environmental conditions.

There was a need for a fuel drying facility with this project, as the exercise required us to cut down trees that I planted 29 years ago for gasifier fuel in 1977. The wood was sliced into 50mm rings then chopped into small blocks.

The dryer was made using an elliptical tube heat exchanger, heated by the 260°C engine exhaust. Air was blown into a chamber under the sloping exchanger that was collected from a simple box mounted around the engine. This provided a waste heat flow of 50°C and provided a real bonus to dry the green and very wet fuel blocks. This took about 8 to 10 hours of drying time.

Even though the installation was located out in the open, the close proximity of the gasifier and engine, created a very heated work area, and provided an indication of just how much waste heat could be recovered from such a small system. This does improve the economics of investing in this technology, but not all locations need waste heat, but its recovery for drying fuel wood, should be seriously considered.

Although not perfectly set up as one would install a permanent system, it is useful to see in a training situation, just how well the small gasified power stations can function. The whole system is manual without any sophisticated control systems. Most rural generation is operated morning and night, so an operating period of 4 hours from a single manual filling of the hopper, enables its operation with a minimum of attendance.

Gasified power generation needs a regular discipline of operation, and in return provides reliable performance.
Here are a few details:

Daily service: Clean out waste char – 5 minutes..
Change filter sawdust – 10 minutes.
Check engine oil/water – 5 minutes.
Refill fuel hopper to start – 5 minutes.

Gasifier ignition – 10 seconds.
Gas ignition at test flare – 2.5 minutes.
Engine start – 3 minutes.
Full power generation from start – 4 minutes.
Total system pressure drop – l.5”W.G.(37mmWG)

Making wood block fuel for gasifiers may be an onerous task, but remember a 20 litre bucket contains about 5-6 kg of wood, which can do the same work as about 1.6 litres of diesel fuel, slightly more for gasoline. It therefore is reasonable to say that it has the same value as liquid fuel for power generation, and has a value of $2.40 per bucket at the moment here in New Zealand. This would put a value of $400 per tonne, but in rural locations world wide, it would represent considerable savings, while providing useful employment and income for local labour.

The most important consideration for gasified power generation is to begin planting your fuel wood trees now, because you are surely going to need them within the next 30 year time span.

The following photographs show the temporary installation and its location on my 10 acre block. I erected a simple tarpaulin cover over the equipment just to keep the sun and rain off for the two weeks while in use. Consideration is now being given to create a permanent training facility under cover inside the shed.

 

View from the installation.
Looking down on the installation with the fuel wood trees cut down immediately on the left.
Wood dryer on the left, engine generator in the centre, and gasifier on the right.
Dryer during construction showing sloping heat exchanger that was covered with l/2 bird wire to stop wood falling through tubes
Finished dryer with sliding doors on front to remove dried fuel.
Large fan draws 50°C waste heat from engine via yellow flexible hose for discharge into chamber under heat exchanger. The large fan also provided a large electrical load for the engine generator so that it could be operated towards its maximum output.
Pioneer gasifier manufactured in 1987
50mm slices cut from the branches of the parent pine tree
Chopped blocks compared to hand size
Hopper with rapidly drying fuel.
Training underway with explanation of cooling system
Igniting the gasifier for start-up.
Clear smiles of relief from trainees at successful start-up.