The U.S. Department of Energy (DoE) has challenged manufacturers to accelerate the development of heat pumps that can perform well in colder climates.
As part of its Initiative for Better Energy, Emissions, and Equity (E3 Initiative), the DoE’s Residential Cold Climate Heat Pump (CCHP) Technology Challenge seeks to demonstrate performance in the lab and at pilot sites before implementing new technologies in the market.
Nominal capacity requirement
To meet the DoE CCHP Challenge, a heat pump 4 tons and lower must have a coefficient of performance (COP) of 2.4 while providing 100% of nominal rated capacity at an ambient temperature of 5 degrees F. A heat pump larger than 4 tons must have a COP of 2.1 with the same nominal capacity requirement at 5 degrees F.
There are no products on the market that currently meet these performance specifications
In addition, the heat pump must have an HSPF2 = 8.5 in Climate Zone 5 (a cold northern climate where annual minimum temperatures range between negative 20 and negative 10 degrees Fahrenheit). There are no products on the market that currently meet these performance specifications. COP is the relationship between the power (kW) that is drawn out of the heat pump as cooling or heat, and the power (kW) that is supplied to the compressor. HSPF2 is a factor evaluating the efficiency of a heat pump during cold weather, measured according to the DoE’s new, more accurate scale.
Cascade refrigeration systems
There are several approaches to improving a heat pump’s performance in cold climates, including cascade refrigeration systems, various forms of multi-stage compression, vapor-injection, and liquid injection. The optimal solution will consider the trade-offs among customer needs, product cost, operational efficiency, reliability, and technology readiness. “It’s all about maximizing value for our customers while meeting their comfort needs,” says Katie Davis, Vice President of Engineering and Technology, Residential HVAC, Trane Technologies.
Trane tested its CCHP prototype at the DOE’s lab, the Oak Ridge National Lab Facility. The prototype performed in temperatures as low as negative 23 degrees Fahrenheit, surpassing the mandatory negative 20 degrees Fahrenheit DoE requirement. “Our prototype pushed the limits of the testing with high performance even as temperatures moved beyond the trial scope,” says Davis.
| Trane tested its CCHP prototype at the DOE’s lab, the Oak Ridge National Lab Facility |
Ambient operating conditions
“Passing the lab testing phase means we’re now able to conduct field testing with this heat pump, which will provide us with the opportunity to keep a family warm this winter,” says Davis.
Trane’s unit will begin field testing in Boise, Idaho. The prototype will be placed in cold climate ambient operating conditions in a residential building. For Trane’s current CCHP prototype, the DoE may decide to extend the field trial testing into a second heating season. If this is the case, Trane will participate in the second field trial in 2023. If field trial testing concludes in 2022, Trane will continue toward the commercialization of the product
Vapor compression cycle
Colder ambient temperatures require changes to the vapor compression cycle
Colder ambient temperatures require changes to the vapor compression cycle utilized in a heat pump to provide the heating capacity required at 5 degrees F and below. Compression technology has now advanced to the point where this capability can be incorporated into the system to provide the additional capacity required.
Currently for residents in colder areas of the country, and until newer technology comes to market, a heat pump might be the right choice when matched with a furnace or other electric heating device. This way, a home will continue to stay warm on the coldest days or run more efficiently for most of the season.
Environmentally minded furnaces
Compared to a traditional furnace and air conditioner heating and cooling setup, heat pumps can save as much as $526* a year in energy costs. They also emit zero of the harmful emissions that have been proven to contribute to climate change.
(*Estimated cost savings are based on ENERGY STAR's Savings Calculator for a 3-ton 21 SEER/10 HSPF heat pump and programmable thermostat versus the industry standard 14 SEER/8.2 HSPF 3-ton heat pump and standard thermostat in St. Louis, Mo.)
Trane continues to provide the most efficient options available including heat pumps
Trane continues to provide the most efficient options available including heat pumps, more environmentally minded furnaces, and the pairing of the two in dual-fuel systems. Like a hybrid car that runs on electricity when possible and switches to gas as needed, a dual-fuel system runs the electric heat pump as often as possible and switches to the gas furnace when needed.
Other electrification incentives
Hybrid systems offer those homeowners a way to adopt a heat pump and reduce their carbon footprint at a much lower total cost while keeping the safety net of a gas furnace, especially for those in colder regions of the country.
The most efficient heat pumps, like the Trane Platinum XV20i Heat Pump, can operate in temperatures as low as 0 degrees Fahrenheit. The recently passed U.S. Inflation Reduction Act (IRA) and other electrification incentives that exist in some markets will make heat pumps very attractive, even for homes that currently have a gas furnace.
| Hybrid systems offer those homeowners a way to adopt a heat pump |
Variable speed HVAC systems
Homeowners seeking out sustainable solutions like heat pumps are becoming increasingly aware of governmental perks and tax rebates to reduce fossil fuels. They can take advantage of new clean energy tax credits and rebates available through the IRA, which includes an expansion of the Energy Efficiency Home Improvement Tax Credit (25C) and an extension and expansion to the New Energy Efficient Home Tax Credit (45L).
The Trane Platinum XV20i Heat Pump is part of a new line of equipment featuring Trane Link, a communication technology designed to simplify installation, commissioning, and remote monitoring of Trane’s variable speed HVAC systems. Following a successful regional launch in spring 2022, the full line of Trane Link equipment will be available for Trane’s independent dealers to order nationwide beginning this month.