Eleven utility thermal energy network pilots were on the table in New York; two go ahead. The state's Public Service Commission authorised the pair on 15 October with a combined budget of $111.5 million, of which $93 million comes from the state's Sustainable Futures Program, and declined the other nine, which together had asked for more than $1 billion of ratepayer money. OilPrice returned to the decision on 8 November.
Buffalo: four pipes
National Fuel Gas Distribution is authorised to spend $61.4 million in downtown Buffalo. Its network uses a four-pipe configuration to supply heating and cooling to 12 affordable multifamily buildings and one municipal building. The heat comes from wastewater influent and geothermal boreholes, and the scheme displaces hot water boilers in the existing Buffalo District Energy System, according to the Commission's release.
Haverstraw: one pipe
Orange & Rockland's West Loop project in the Village of Haverstraw is authorised at $50.1 million. Here a single-pipe ambient temperature loop links municipal, commercial and residential buildings across roughly 10 acres. Two geothermal borefields and a wastewater heat exchanger feed the loop, which provides heating, cooling and domestic hot water. OilPrice describes the connected buildings as including single- and multifamily homes and an elementary school, and the technology as electric heat pumps taking the place of gas boilers and furnaces.
The Commission's chair said more than 80% of the project costs are secured through the state fund. The order also tells department staff to collect lessons from the two pilots for future proposal guidance and for a Thermal Energy Network Roadmap called for in the State Energy Plan. Neither source gives a construction schedule.
Two layouts, two kinds of building connection
Nobody planned it as an experiment in hydraulics, but that is what the pair amounts to. A four-pipe network carries hot and chilled water separately, at temperatures a building can use more or less directly; the plant is central, and the building connection is a pair of heat exchangers with control valves. A single ambient loop carries lukewarm water that is neither. Every building needs its own heat pump, and the loop only has to stay within the band those machines accept.
Sewage is the common source. Raw wastewater is a good heat carrier and a poor neighbour for a narrow channel: fibres, grease and biofilm. The exchanger on that side is usually a fouling-tolerant design with regular cleaning, and a clean intermediate circuit keeps the sewage away from the network water. Between that circuit and the loop, and again between the loop and each building, ordinary plate heat exchangers do the separation.
For operators, the thing to watch in Haverstraw is what every ambient network meets after a few winters: whether the heat taken out in the cold months balances what is put back in summer, and who pays for the pumps when it does not.
Sources: New York State Department of Public Service, OilPrice
