Dal AC is taking its place on the cutting edge of clean energy technology with its fully-retooled Biomass Energy Plant.
The restored plant burns mostly sawmill residue using hot gas to warm up thermal oil, feeding heat energy into the plant’s new organic Rankine cycle (ORC) system that drives the turbine. Dalhousie is the first university in North America to use the technology in burning wood fuel.
“We have been approached by other universities across North America because they’re interested in the technology itself and how we have implemented it on our campus,” said Dr. David Gray, Dean of Dalhousie Agricultural Campus. “Our aspiration and our goal is to be a carbon-neutral campus. We have not set a target on that, but we’re certainly hoping within the next 10 years we’ll be carbon neutral.”
The $26.5-million plant was upgraded from an old wood biomass steam boiler to the present thermal oil heater using ORC technology. Wood fuel is fed into the plant’s two new storage bays by trucks and is moved into the thermal oil heater by floor rakes, levelling screws and a chain conveyor system.
Once fuel reaches the heater, the ORC system works by transferring hot gases produced by the burning wood chips into a closed oil loop using a heat exchanger. This heat is then transferred to the oil fluid, causing it to vaporize. The vaporized fluid expands and pushes the plant’s 1 MW turbine, creating electricity.
Next, the oil vapour is condensed and its heat is transferred to the campus district hot water system. Lastly, the cooler thermal oil returns through the closed loop to start the cycle again.
The plant’s new hot water distribution system is 30 per cent more energy efficient than the former steam system. Sixteen energy transfer stations were converted from steam to hot water and another 2.6 km of hot water pipes were installed.
To further combat air pollution, the plant has installed an electrostatic precipitator to remove harmful gas particles using electrically-charged plates.
Wood ash generated by the renewed plant will amount to about 400 tonnes per year and is used as farm fertilizer.
“This is a great example of Dalhousie’s ongoing commitment to sustainability and energy efficiency,” said Minister of Lands and Forestry Iain Rankin in a release.
As well as supplying energy to the Dal AC campus, the plant sells electricity to the Nova Scotia Power grid under the province’s Community Feed-in Tariff (COMFIT) program at a rate of 17.5 cents per kilowatt-hour. The restored plant began producing electricity in June and can meet up to 75 per cent of Dal AC’s energy needs.
“Our campus continues to be our largest classroom and exposing our students to state-of-the-art technology and innovative solutions to real world problems remains a priority,” said Gray.
The university is already researching more expensive fuels that could provide a sustainable fuel source in future – one research project will look into the feasibility of growing and burning willow, which is fast growing, absorbs water and grows well in marginal lands not suitable for food production crops.
The second study will look at using the wood from selective harvests and silviculture.
Gray added that Dal AC is also aiming to install solar and wind energy technology on its campus, and focus on sustainable farming.
