Monday, March 15, 2010

Behind the scenes tour

Today's first activity was to take a tour with Jo Gwillam, CAT education staffer and renewable energy expert, Jo Gwillim.

Jo took us into some very rarely visited corners of the CAT site, where we were able to get up close with some fairly high tech equipment.

We started with the new wood chip combined heat and power district heat plant. The first picture is the input fuel elevator. This uses what would generally be low grade or even waste wood for fuel, making a rated output of 100 KW of electrical power and 250 KW of heat (about 850,000 BTUs -- enough to heat our gym/Activities Building and perhaps our library too). The equipment was of Czech manufacture, and cost around a million pounds ($1.5 million) all told according to Mike, the engineer in charge of running it.

The CAT engineers are still fine-tuning the output, both heat and power, and say that the thermodynamic efficiency so far is only 60% or so, but that's still way better than the 35% of an internal combustion generator system, although not as good as a pellet fuel furnace. They hope to get the number up. Even so, the fact that it uses low grade fuel makes it probably cost effective. The theoretical efficiency of a CHP system can be as much as 80%. Natural gas or bio-sourced methane systems can be up to 90% but they have more reliable fuel quality.

A good comparison in terms of rated output would be that this million pound rig is the equivalent of three 100KW wind turbines (say Northwind 100s) at around £350,000 ($500,000) each, at a 33% capacity factor, and a million BTU oil furnace for say £20,000 ($30,000). So compatible, price wise, with the cheapest form for 100KW of renewable energy and the cheapest form of fossil-based Maine space heating.

Except you can have renewable heat and power whenever you want, not just when the wind blows. If we let the manufacturers and bleeding edge early adopters like CAT work out the kinks, and if the price came down to say 50% we could almost afford to get one of these for the offset cost of Activities Building and Library heat oil, and power for the rest of campus.

Here's the generator (second picture). Very shiny. So far they've only managed 75KW/hour, but they hope to get that up.

This is not a gasifier/combined cycle system. There's a heat exchanger to take off the heat and make clean expanding hot air for the turbine.

The CAT engineers have put in this thermal storage system (third picture) for the district heat side of the CHP plant, to even out the heat usage over time. This is a large scale version of what our friends at Revision Energy have been doing at the household scale with pellet furnaces and solar thermal systems.

Then Jo showed us the cliff railway system, which uses a water balance counterweight -- no energy required. They use a regenerative braking system that makes compressed air for power tools, so this is really a "hybrid" cliff railway. The lumber is 100% local, green lumber, air-dried. The railway's upper building was built by a women-only crew.

We then visited this 7KW solar breezeway attached to the restaurant, where there is an interesting kind of see-through solar module, with very nice dappled light pouring into this outdoor hang-out space. Not too bright you couldn't use a computer, not likely to get too hot in summer, but still very well lit naturally, and generating power too. Cost around £7 per installed watt, ways Jo.

I want one of these for our campus. We probably couldn't afford to buy this many modules, and it would be a waste of money since we already run on Maine-made wind and hydro power, but we could perhaps make them for about a tenth of the cost from "raw" solar cells and glass much as we did in this laboratory exercise here. And the facility would be a nice outdoor hang-out or even classroom space.

We then hiked up to the reservoir for the hydro power system, which has brown trout, apparently, which caught the attention of a few of our outdoors types.

Finally we went up to the lowest of the wind power sites, where we saw a Proven downwind machine, and a small scale older machine whose name escapes me, as well as anemometry systems, including a model #40 anemometer from our friends at NRG Systems.

The last photo is of the Nordtank machine high above CAT which Jo says is around 225KW rated output and community-owned. It has an advanced form of stall control based on pivoting blade tips, which I found intriguing.


  1. I'm so jealous. Hope you're havin' a blast.

  2. I am, and the students seem to be.

    A handful are so very fond of their low-carbon vegetarian lunches, though!