Today I visited my friend Andy at his CSA outside of Boston, to get a tour and help diagnose some issues he’d been having with the cooling system in one of his greenhouses. The farm is in a suburban neighborhood on the site of a former agricultural research station (home of a famous butternut squash), which has fallen somewhat into disrepair, with several decrepit metal-and-glass greenhouses – apparently they were built with toxic putty, toxic insulation, and fly ash in the concrete, a whole panoply of environmental headache. The overall effect of barren winter fields, abandoned buildings, looming smokestack, and decaying glass houses behind chain-link fence gave a distinct post-apocalyptic flavor – and apparently film students have actually used the site for that purpose:
But the action is out in the fields, on 8 flat, productive acres, where Andy and friends turn minimal infrastructure into serious agriculture, producing several hundred shares for a popular CSA, and providing fresh produce for local charities as well. We saw their fields, including cover crops already starting to re-awaken, compost piles, greenhouses, small homemade cooler building, and tractor shed, where they keep a couple old cultivating tractors and an array of specialty implements, many of which are the better part of a century old:
They also have a couple of newer 40hp tractors for PTO implements in one of the greenhouses. The second greenhouse was the focus of our afternoon’s efforts; it didn’t have as much cooling power as the first (reference) greenhouse, despite being larger, and my job was to figure out why. The reference greenhouse had two thermostatic switches; the first of which opened one louver at the west end of the greenhouse and turned on one fan at the east end to exhaust heat. The second thermostat, set to a higher temperature, opened two more louvers, increased the speed of the fan that was already running, and turned on a second fan.
The second greenhouse also had two thermostatic switches in a similar configuration, but only one of them had a discernible effect, which was to open all three louvers and turn on two relatively tepid exhaust fans at the far end. Andy assumed (reasonably) that the second thermostat was supposed to have the same effect in that greenhouse as the equivalent one did in the reference greenhouse, but had not been able to get it to do anything.
We opened up the thermostatic controls, and determined that the second thermostat wasn’t doing anything – its relay terminals weren’t wired to anything; in fact the only thing wired to it was 120V power. Then the question became whether the fans at the other end of the building had the capability to run faster, that was simply not wired. We opened up their junction boxes, and determined that they only had two wires plus ground (live and neutral); then we inspected the motors, which were just plain half-horse 1725 rpm induction motors. By comparison, the motor on the reference greenhouse had three wires plus ground (presumably high, low, and neutral), and were substantially larger as well.
So, that part of the mystery was solved – the greenhouse had never had adequate cooling – and it would require at least a different motor (and probably a whole new exhaust fan unit) to upgrade it. We then looked at the much smaller internal circulating fans on the greenhouse – the ones on the north side worked normally, but the ones on the south didn’t work at all. We traced the power from the circuit breaker to the fan junction box, and found the problem in a cheap solid state speed control that was wired in series with the fans. We then shorted across it, which caused one of the fans to come on, but not the other. The other got hot when powered up, though, and the shaft turned, but with significant friction – and that solved the mystery of what killed the speed control: a bearing seized in one of the fans, which increased the current, and fried the speed controller. We set it up so the one circulation fan could run at full speed, and shut off the other – hopefully Andy can find a new motor for it, or just replace the unit.
Meanwhile, I’ve been horrified and transfixed by the images of an actual apocalypse underway in eastern Japan, complete with walls of muck and embedded burning structures racing across the countryside, exploding natural gas tank farms, and smoldering nuclear plants. The human tragedy, loss of life, and physical destruction are truly staggering. We are used to disasters happening in far-off lands, often in relatively undeveloped circumstances – but Japan is every bit as modern as the US. Some years ago I spent some time doing engineering in Japan, living for a few weeks in a seaside town effectively interchangeable with those that have been completely destroyed. I found the people friendly, generous, and civilized almost to a fault – and I have no doubt that their disaster response is at least as capable as would be mustered here, but any human effort pales against the magnitude of the destruction that has been unleashed. In our tightly optimized, risk-averse normal mode of life, it is easy to forget how indifferent and utterly inhospitable the vast majority of the universe is to the needs of a fragile hairless ape.
Although the nuclear angle is unlikely to even register on the total death toll from the disaster, the struggle to maintain control of the reactors is especially captivating to an engineer. I grew up just five miles downstream from a nuclear power station of similar vintage to the Japanese plants (a PWR, not a BWR), which was permanently shut down for safety problems. As a student Alexis briefly considered taking a job at MIT’s nuclear reactor – she needed money, and they would basically pay students good wages to study and sit for the NRC reactor operator’s license. I’m trying to imagine what sort of effort is happening on the ground there – are they sitting in the classic movie set control room throwing switches? Or is that control room full of muck and lobsters, and they are desperately trying to unbury the junction box enough to hot-wire the feedwater pumps? How do you plumb seawater into the core of a nuclear reactor? Is there a fireman’s connection somewhere, and guys are hooking up a giant trash pump with a tube into the murky sea? Or is it already plumbed for that eventuality? And the probablistic nature of radiation sickness adds a certain poignancy – there’s a smooth Shrodinger’s cat gradient from “these levels are significantly above background, but hopefully I won’t get cancer” to “I’m a dead man walking, I guess my duty is to keep this plant from poisoning my fellow citizens”.
There’s also the question of how all this plays into the global energy situation, already reeling from revolutions in 3 Middle Eastern countries (and counting). In the last year we’ve seen riveting disasters associated with three top sources of energy (coal mine disasters, gulf oil disaster, now nuclear reactor meltdowns). While lots of folks are uncomfortable with nuclear power, it seemed like things were moving in the direction of resignation, with many people accepting that increased use of nuclear might be a lesser-of-evils calculation, as part of a multi-pronged approach to tackling climate change. As a renewable energy engineer, I have a hard time getting behind nuclear power, and it’s basically impossible to see it as a workable solution on a global scale, given the degree of instability in many parts of the world and attending proliferation risk. But regardless of its actual cost/benefit breakdown, it’s easy to see the partial meltdown of multiple nuclear reactors as putting the kibosh on a nuclear renaissance for many years. Nuclear already faced an uphill battle, because of NIMBYism, high capital costs, cheap natural gas, etc.