Jane Melia, co-founder and CEO of Harvest, discusses the advantages of teaming a high-end eat pump with a large thermal battery, to coordinate the timing of electricity consumption. Shifting the heat pump load can help reduce both costs and emissions.
We have an antique house in Vermont, and installed geothermal last year. We didn't have ducts and don't have room to add any. However, we do have antique cast iron hot water radiators. It turns out those radiators make *exceptionally good* thermal batteries. They're coupled with a 50 gallon, highly insulated water tank.
We have battery backup for the house, as part of a virtual power plant program by our electric utility. The power company can draw from them during peaks to offset peak load at nearby homes). The geothermal pump isn't backed up by the batteries, but the interior circulator pumps that feed hot water through the radiators are backed up. During a power outage last winter, we found that as the water continued to circulate through the house, the latent heat in the water, combined with radiators' thermal mass kept the house warm for 11 hours on a 23°F day. The house hadn't been insulated, yet, so I imagine now that it's insulated, we may end up with enough latent heat to keep the house warm for 15 or more hours.
Additionally, due to the slow release of heat from the radiators over time, the house doesn't go through the typical overheat-overcool-overheat cycles from the old oil boiler, making it much more comfortable. Despite some very cold overnights, the geothermal never had to run above its lowest power level.
Our heating costs dropped from $730 - $1130/mo for oil & propane down to $230 - $280/mo. The payback period for the geothermal is going to be much quicker than we had estimated, and I'm sure the thermal battery effect from the radiators' thermal mass is a big part of that.
We also replaced our propane hot water heater with a heat pump one. We're remodeling our kitchen at the moment, and will be arranging the ducts for the water heater to blow cold air behind the refrigerator, and pull warm air from behind the oven. We don't know what the impact will be overall, because we don't use the oven that much, but hopefully, it'll result in a net power savings overall.
This was SOOO cool! Going to inquire more, and met someone on our ND who has this (I posted a link to this podcast there). Question: would it ever make sense to store coolth? Another tank of this time cold water?
I want one. Or two. (I think my house needs more than one outdoor unit in the sizes SanCO2 makes) I've kinda thought about doing something similar but it would be a science experiment needing a really committed plumber and a sheet metal company to put in the fan coil.
I know buildings around here using SanCO2 for DHW only. They work great. One nice thing alluded to is that by keeping all the refrigerant in the outdoor unit, you don't need a refrigerant-certified installer.
I worked on residential solar thermal heat/DHW years ago. Some of our systems weren't too different.
I am building a new house in Maine and we have designed a system similar to this. But Maine has a lot of homes with hot water radiators and it has been a tough nut to crack. Efficiency Maine is running a pilot very similar to this- they should connect to them.
This is what I came here to say. In the Northeast we have a lot of radiator / hot water systems. Many converted from steam, and now run gas fired hot water. So if you're targeting existing structures, it's helpful to know whether the system works with hot water radiators. It seems that forced hot water systems are designed to provide water at 180° and in the podcast it seems like 150° in the hot water tank. A longer cycle time, a slow warming house, maybe too much of a difference?
Folks, the Harvest system circulates potable (drinking) water to the storage tank and coil in the fan coil. So unless another HX is installed (between potable and heating HW) it won't be utilized with existing HW systems. I think even the fan coil coil needs a special rating for use with potable water.
There are other companies making water-water (for "geo") and air-water heating heat pumps. These may also heat domestic HW through another HX or not. In the EU, there are many many models to choose from, often utilizing a similar outdoor unit design (all the refrigerant is factory sealed there; heating water comes in an out of the building). They call them "monobloc" and in many cases utilize propane (R-290) as the "refrigerant."
Generally providing 160F HW in the high temperature versions, but most of EU experience subzero outdoor temps and their HW systems have generally utilized this slightly cooler water.
It's nice to read of folks using 140F water in their ancient radiators. American "baseboards" are a bigger problem.
We did an experiment with our heating system before installing the geothermal. We turned the oil boiler down to its lowest heat setting (140°F) for the winter before to verify that the house would remain warm. It did. That was what we needed to confirm that a heat pump system could work. Interestingly, the geo is set to provide 120°F water, and it still worked perfectly. We couldn't be happier!
I used comfort-craftsmen.com to install Air to Water Heat Pump with no modification to fin tube baseboards from 1989. Water tank ranges from 90 - 130F. Moderate air sealing and cellulose made it possible. gas meter is gone & last 2 winters were great.
We have an antique house in Vermont, and installed geothermal last year. We didn't have ducts and don't have room to add any. However, we do have antique cast iron hot water radiators. It turns out those radiators make *exceptionally good* thermal batteries. They're coupled with a 50 gallon, highly insulated water tank.
We have battery backup for the house, as part of a virtual power plant program by our electric utility. The power company can draw from them during peaks to offset peak load at nearby homes). The geothermal pump isn't backed up by the batteries, but the interior circulator pumps that feed hot water through the radiators are backed up. During a power outage last winter, we found that as the water continued to circulate through the house, the latent heat in the water, combined with radiators' thermal mass kept the house warm for 11 hours on a 23°F day. The house hadn't been insulated, yet, so I imagine now that it's insulated, we may end up with enough latent heat to keep the house warm for 15 or more hours.
Additionally, due to the slow release of heat from the radiators over time, the house doesn't go through the typical overheat-overcool-overheat cycles from the old oil boiler, making it much more comfortable. Despite some very cold overnights, the geothermal never had to run above its lowest power level.
Our heating costs dropped from $730 - $1130/mo for oil & propane down to $230 - $280/mo. The payback period for the geothermal is going to be much quicker than we had estimated, and I'm sure the thermal battery effect from the radiators' thermal mass is a big part of that.
We also replaced our propane hot water heater with a heat pump one. We're remodeling our kitchen at the moment, and will be arranging the ducts for the water heater to blow cold air behind the refrigerator, and pull warm air from behind the oven. We don't know what the impact will be overall, because we don't use the oven that much, but hopefully, it'll result in a net power savings overall.
This was SOOO cool! Going to inquire more, and met someone on our ND who has this (I posted a link to this podcast there). Question: would it ever make sense to store coolth? Another tank of this time cold water?
I want one. Or two. (I think my house needs more than one outdoor unit in the sizes SanCO2 makes) I've kinda thought about doing something similar but it would be a science experiment needing a really committed plumber and a sheet metal company to put in the fan coil.
I know buildings around here using SanCO2 for DHW only. They work great. One nice thing alluded to is that by keeping all the refrigerant in the outdoor unit, you don't need a refrigerant-certified installer.
I worked on residential solar thermal heat/DHW years ago. Some of our systems weren't too different.
I am building a new house in Maine and we have designed a system similar to this. But Maine has a lot of homes with hot water radiators and it has been a tough nut to crack. Efficiency Maine is running a pilot very similar to this- they should connect to them.
Thank you Jane and David! Here is hoping Harvest flourishes and grows quickly. It cannot happen soon enough.
This is what I came here to say. In the Northeast we have a lot of radiator / hot water systems. Many converted from steam, and now run gas fired hot water. So if you're targeting existing structures, it's helpful to know whether the system works with hot water radiators. It seems that forced hot water systems are designed to provide water at 180° and in the podcast it seems like 150° in the hot water tank. A longer cycle time, a slow warming house, maybe too much of a difference?
Folks, the Harvest system circulates potable (drinking) water to the storage tank and coil in the fan coil. So unless another HX is installed (between potable and heating HW) it won't be utilized with existing HW systems. I think even the fan coil coil needs a special rating for use with potable water.
There are other companies making water-water (for "geo") and air-water heating heat pumps. These may also heat domestic HW through another HX or not. In the EU, there are many many models to choose from, often utilizing a similar outdoor unit design (all the refrigerant is factory sealed there; heating water comes in an out of the building). They call them "monobloc" and in many cases utilize propane (R-290) as the "refrigerant."
Generally providing 160F HW in the high temperature versions, but most of EU experience subzero outdoor temps and their HW systems have generally utilized this slightly cooler water.
It's nice to read of folks using 140F water in their ancient radiators. American "baseboards" are a bigger problem.
We did an experiment with our heating system before installing the geothermal. We turned the oil boiler down to its lowest heat setting (140°F) for the winter before to verify that the house would remain warm. It did. That was what we needed to confirm that a heat pump system could work. Interestingly, the geo is set to provide 120°F water, and it still worked perfectly. We couldn't be happier!
Thanks, good to hear!
I used comfort-craftsmen.com to install Air to Water Heat Pump with no modification to fin tube baseboards from 1989. Water tank ranges from 90 - 130F. Moderate air sealing and cellulose made it possible. gas meter is gone & last 2 winters were great.
Would there be any advantage to dumping the heat removed by the (separate) Air Conditioner into the Harvest water tank? Or is that overkill?