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Credit: Dieter Nagl

Buildings and Cities

Heat Pumps

Robert Simmer, director of Stadtwerke Amstetten, a local utility company in Austria, stands in front of a heat pump designed to capture and recycle energy from the sewer.

The building sector worldwide uses approximately 32 percent of all energy generated; more than one-third of that is for heating and cooling. Maximum efficiency in heating and cooling could cut energy use by 30 to 40 percent.

The means to increase efficiency are at hand, and one technology stands out from the rest: heat pumps. Like a refrigerator, a heat pump has a compressor, condenser, expansion valve, and evaporator, and transfers heat from a cold space to a hot one. In winter, that means pulling heat from outside and sending it into a building. In summer, heat is pulled from inside and sent out. The source or sink of heat can be the ground, air, or water.

While cost can be high and efficiency fluctuates depending on local climate, heat pumps are easy to adopt, well understood, and already in use around the world. They can supply indoor heating, cooling, and hot water—all from one integrated unit. When paired with renewable energy sources and building structures designed for efficiency, heat pumps could eliminate almost all emissions from heating and cooling.

References

Benjamin Franklin…science of refrigeration: Isaacson, Walter. Benjamin Franklin: An American Life. New York: Simon and Schuster, 2003.

“possibility of freezing a man to death”: Franklin, Benjamin. Letter to John Lining. London, June 17, 1758.

air-conditioning…“epidemic”: “No Sweat.” Economist. January 5, 2013.

understand how this happened: Cooper, Gail. Air Conditioning America: Engineers and the Controlled Environment, 1900-1960. Baltimore: The Johns Hopkins University Press, 1998.

road civilization should never have taken: Cox, Stan. Losing Our Cool: Uncomfortable Truths About Our Air-Conditioned World (and Finding New Ways to Get Through the Summer). New York: The New Press, 2013.

[predicted] increase in AC demand: Henley, John. “World Set to Use More Energy for Cooling Than Heating.” The Guardian. October 26, 2015.

[growth of] air-conditioned homes in Chinese cities: “No Sweat,” Economist.

China will [become] leading consumer of AC: Cox, Stan. “Cooling a Warming Planet: A Global Air Conditioning Surge.” Yale Environment 360. July 10, 2012.

building sector…energy…for heating and cooling: Lucon, O., D. Ürge-Vorsatz, A. Zain Ahmed, H. Akbari, P. Bertoldi, L. F. Cabeza, N. Eyre et al. “Buildings.” In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, and New York: Cambridge University Press, 2015.

unit of electricity consumed…five units of heat energy…transferred: IEA. Transition to Sustainable Buildings Strategies and Opportunities to 2050. Paris: International Energy Agency, 2013.

[potential to] reduce…emissions: IEA HPC. Retrofit Heat Pumps for Buildings. Boras, Sweden: IEA Heat Pump Centre, 2010.

view all book references

Technical Summary

Heat Pumps

Project Drawdown defines heat pumps as: high-efficiency [1] electrical devices that harvest latent heat from ambient sources such as the ground, air, or water for use in the conditioned space via the compression and expansion of a working fluid (refrigerant). This solution replaces new and existing conventional heating, ventilation, and air conditioning (HVAC) systems, including gas- and oil-fired furnaces, gas- and oil-fired boilers, room air conditioners, central air conditioners, electric resistance furnaces, and electric resistance unit heaters in both residential and commercial applications.

Methodology

Total Addressable Market [2]

The total addressable market for heat pumps is considered to be the global final energy use for residential and commercial space heating and cooling, derived from the International Energy Agency’s 6°C Scenario (IEA, 2016). In the absence of reliable data, it was assumed that the residential sector comprises 75 percent of the global market, with the remaining 25 percent attributed to the commercial sector. Current adoption [3] of high-efficiency heat pumps was estimated to be 0.02 percent of the market.

Adoption Scenarios [4]

Impacts of increased adoption of heat pumps from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.

Data on global adoption scenarios of high-efficiency heat pumps remains sparse. It is estimated that improved HVAC equipment can reduce the overall demand for space heating and cooling from 25-70 percent. Reducing demand by 45 percent, for example, is approximately equivalent to a scenario in which several countries/regions – such the U.S., Canada, EU, Japan, and Australia – adopt high-efficiency HVAC standards. If China were to also adopt the standards, the market share for high-efficiency HVAC would approach 70 percent approximately 20 years after adoption. Although Project Drawdown notes relatively aggressive new efficiency standards, such as the condensing furnace standard in the U.S., a gradual uptake of high-efficiency equipment is assumed, with more aggressive growth globally as prices continue to decrease.

For heat pumps, three scenarios were developed:

  • Plausible Scenario: In the absence of a clear global picture, a Bass Diffusion Model is used to estimate growth optimized to reach 25 percent of global space heating and cooling demand by 2050.
  • Drawdown Scenario: Estimated growth is optimized to reach 45 percent of global space heating and cooling demand by 2050.
  • Optimum Scenario: Estimated growth is optimized to reach 60 percent of global space heating and cooling demand by 2050.

Emissions Model

It is assumed that for every terawatt-hour (therm) produced by high-efficiency heat pumps, an equivalent amount of energy would be generated from conventional fuel combustion (coal, oil, and natural gas only) [5] and low-efficiency electric heating and cooling systems. While the replacement of these high-emissions technologies for electricity-based heat pumps will increase the overall usage of electricity, overall energy savings are achieved through direct fuel combustion and an assumed 60 percent improved efficiency in electricity use.

Financial Model

The first costs of HVAC equipment are estimated at $8,417 per installation unit, compared to a weighted cost of $4,179 per unit for conventional HVAC systems. [6] Costs are equal to the sum of the retail price of the equipment and any material or labor costs necessary for installation. The reported installation costs for conventional and switch technologies are weighted by residential and commercial applications, at 75 and 25 percent, respectively. The source for these values comes from the DOE, EIA, IEA, and International Renewable Energy Agency (IRENA). Data was also collected from current (2016) industry sources for residential heat pumps, but was excluded from the study in order to avoid overweighting the cost of residential installations with unpublished data. However, these data points suggest the decreasing costs of heat pumps, with a difference of $1,644 from the average published cost. This data is used to benchmark a published learning rate for comparable technologies at 9.61 percent (Taylor, 2013).

Operating costs included: building heating and cooling energy (fuel and electricity), and other electricity use. Fuel and electricity prices were averaged over the ten years prior to the base year, and emissions factors were obtained from Intergovernmental Panel on Climate Change (IPCC) guidelines.

Integration[7]

The heat pumps solution was integrated with others in the Buildings and Cities Sector by first prioritizing the solutions according to the point of impact on building energy usage. This meant that building envelope solutions were accounted for first, followed by building systems like heat pumps and district heating, and building controls were addressed last. Thus, the total global demand for space heating and cooling for which heat pumps competes was reduced based on prior energy saving solutions, including insulation, green roofs, and smart glass.

Results

Project Drawdown’s Plausible Scenario adoption of heat pumps avoids over 5.2 gigatons of carbon dioxide-equivalent greenhouse gas emissions by 2050. In addition, implementing heat pumps across the new and existing building stock requires only a marginal investment of US$119 billion more than the Reference Scenario, but saves over US$1.5 trillion in operating costs over 2020-2050. The Drawdown Scenario shows 8.4 gigatons avoided. In the Optimum Scenario, the emissions reduction reaches 11 gigatons.

Discussion

Buildings consume about 31 percent of global final energy use and account for 8 percent of direct energy-related carbon dioxide emissions, putting them among the largest end-use sectors globally. Energy for space heating and cooling is estimated to account for roughly half of the energy consumption in buildings. With an increasing population and rising incomes, it is estimated that the global number of households could grow by over 65 percent and the floor area of commercial and institutional buildings by nearly 200 percent by 2050. In the absence of aggressive policy action for reduced energy consumption, the global cooling and heating energy demand is expected to increase substantially.

Heat pumps can serve as an efficient and sustainable solution to indoor space conditioning with high-efficiency. Retrofitting existing HVAC systems with state-of-the-art heat pump equipment is another viable option for consumers looking for ways to reduce building energy costs, without having to make major investments or structural changes to the building. This may require modifications or additions to the existing system, but offers significant energy savings. In some cases, the new high-efficiency equipment is actually cheaper to install than less efficient equipment.


[1] High-efficiency heat pumps are HVAC systems for heating, cooling, and ventilation with a Seasonal Energy Efficiency Ratio (SEER) of 14.6-23.3, depending on installation (split/packaged).

[2] For more on the Total Addressable Market for the Buildings and Cities Sector, click the Sector Summary: Buildings and Cities link below.

[3] Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.

[4] To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Buildings and Cities Sector-specific scenarios, click the Sector Summary: Buildings and Cities link.

[5] Space heating from biomass is not considered to be replaced by high-efficiency heat pumps in this study.

[6] All monetary values are presented in US2014$.

[7] For more on Project Drawdown’s Buildings and Cities Sector integration model, click the Sector Summary: Buildings and Cities link below.

Full models and technical reports coming in late 2017.

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