Notwithstanding our previously mentioned reservations about ground source heat pumps, For people who live by lakes and rivers they can make a lot of sense. There is no drilling required; just throw the pipe into the lake. But even this simpler system is subject to errors in installation, and all that pipe can disrupt fish habitat and cause other problems.
That is why I was so intrigued when I saw the advertisement for the Limnion Geothermal Transfer System; It puts the entire lake loop into a neat little package that you just drop into the water. When I noticed that it was manufactured the tiny hamlet of Carnarvon, just half an hour from where I spend my summer, I dropped in to take a look and meet the inventors.
Conventional lake loops are laid out on site and ballasted with concrete blocks. But they can still float up and get air traps in them. They can cause problems, as CEO Lorne Heise noted in a press release:
These masses of pipes have a detrimental effect on a sensitive eco system and may destroy aquatic habitats with an ugly and largely non-serviceable coil. These systems are called lake loops and they are becoming an environmental nightmare. The uncontrolled practice of installing bundles of pipe has gone on for years and is currently under review by many environmental authorities in the USA and Canada. The practice has already been banned in many areas as it is not only considered environmentally wrong, it also possesses inherent safety hazards during and after installation as clothing can become tangled in the various caged structures.
The Limnion packs 800 meters (2670 feet) of pipe in 20 meter (66 feet) lengths running between manifolds. Because there are so many pipes but lots of surface area, the unit can support a six ton heat pump with almost no resistance.
Sami recently wrote about how 80% of UK Heat Pumps Are Performing Badly, and I followed up with Lessons From The UK Heat Pump Study: Insulate First And Know What You Are Getting, noting that installations are often less than ideal. I have also quoted John Straube of Buildingscience, who notes that it often takes a lot of energy to pump the liquid through all the pipes, and that "This electrical energy can be significant, particularly if the loop is long, the pipes are small, or the flow resistance within the heat pump unit is large."
But not with the Limnion; They turned it on with test valves on both sides, and the pressure drop was barely a pound. The pumps do not get a workout.
The installer just rolls the thing to the water, hooks up the two pipes, fills the base with two bags of concrete mix and sinks it. No building a mat of pipes at the shore; it is all in one neat little package.
Lorne Heise of Heat-Line discussing the Limnion from Lloyd Alter on Vimeo.
I interview the inventors of the unit here; I apologize for the jittery start, I forgot my tripod and had too much coffee. It settles down. I asked about the environmental effects of all that warm water coming out of the unit in summer, rising out of the unit. Lorne Heise, CEO of the company that makes the Limnion, explains in the video that there is only a four degree difference in temperature, max, and that the volume of water is quite small, rising through the unit by convection only, and that the amount of heat given off by the unit is negligible.
As for winter, I wondered if the unit might not turn into a block of ice as it sucked the few calories of energy out of the lakewater. Fraser Newton and I had some fun discussing the physics of this. In fact, water is densest at 39 degrees, the usual temperature at the bottom of a lake in winter. if you make it cooler it actually rises to the top of the lake, and does not gather around the unit and form a block of ice.
It is an impressive system, designed to be easy and idiot-proof to install, just connect two pipes with twist connectors and fill'er up. The installation issued that have plagued the GSHP industry just go away.
It also goes to prove that the era of the small inventor and manufacturer isn't over; that a small company in the woods of Ontario can come up with a device that significantly improves the state of the art. Heise says: "LIMNION is a timely and necessary key to making geothermal lake systems efficient, affordable, sustainable, safe, easy to install and most importantly - environmentally friendly." And, unlike all those UK heat pump systems, it will probably work as promised.
It is not perfect; CEO Lorne Heise says "Now anyone with a waterfront, riverfront or pond home can heat and cool it without using any fossil fuels." That's not quite true, as the electricity that runs the pumps may well be made with fossil fuels. But they will be using a lot less with this unit, where the pumps don't have to work nearly as hard. Also, most places by lakes and rivers are far from the natural gas lines, and have to burn oil or propane, which is dirtier and more expensive. Many people burn wood, which creates significant local pollution. This is a big improvement over all of those.
