It’s a marriage made in heaven: Solar PV and Geothermal Heat Pumps
Part 2 of a 6-Part Series
Prevailing Heating Technologies
Right now, in our eagerness to generate renewable electricity, we’re overlooking our need to find renewable methods to heat indoor spaces. How can we offset the ancient role of fire in keeping us warm when it’s cold outside?
Perhaps we cling to ancestral ways of heating with fire dating back to the Stone Age because “we’ve always done it that way.” But whether you heat with fuel oil, natural gas, propane, wood or coal you are burning finite natural resources to generate heat, while also producing combustion gases that are implicated in climate change.
Some people think replacing fossil fuel-based heating with renewable, electric-powered equipment would require an unprecedented amount of work and unimaginable amounts of money. But that just isn’t so!
Heating technologies have been evolving for two centuries. For the longest time wood was the fuel of choice burned in fireplaces, then coal. Then came central heating with coal, followed by a switch to heating oil and then to natural gas. With heating equipment having a useful life expectancy of 20 to 25 years, each time a unit is replaced there is an opportunity to upgrade to the latest technology.
Now that we are aware of combustion’s effect on air quality and climate change, even natural gas—the cleanest burning of fossil fuels—is no longer considered the best option. Heating without fire eliminates on-site release of greenhouse gases linked to climate change. Stringent greenhouse gas emission reductions are recommended by the Intergovernmental Panel on Climate Change in order to limit average temperature increases to under 2°C (3.6°F) by 2100 (https://www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_technical-summary.pdf).
President Obama has issued an ambitious executive order to cut the Federal Government’s greenhouse gas emissions by 40% from 2008 levels over the next decade. California, too, recently set its greenhouse gas reduction target of 40% below 1990 levels by 2030 (https://www.gov.ca.gov/news.php?id=18938). In addition, the 2015 New York State Energy Plan recently adopted the goal of reducing greenhouse gas emissions 40% below 1990 levels by 2030, and 80% by 2050 (http://energyplan.ny.gov/Plans/2015). New York City has also mandated a reduction in fossil fuel use by 80% by 2050 (http://www1.nyc.gov/office-of-the-mayor/news/451-14/mayor-de-blasio-commits-80-percent-reduction-greenhouse-gas-emissions-2050-starting-with/#/0).
Today, the trend is clear: electricity use is on the rise and will eventually and inevitably replace fossil fuels. Soon, the question won’t be “whether” we use electricity for heat, but rather “how” we use it. Heating without fire will become the norm and on-site combustion will become a thing of the past.
Returning to the renewable energy equation: Is there a renewable heating, ventilation, and air conditioning (HVAC) technology that can solve the heating half of it?
We need to be able to heat buildings in an economically viable and environmentally sensitive way using renewably-generated electricity.
What about solar thermal, a heat-based technology that warms water, or another fluid such as glycol, to produce hot water? So far, this technology has not been able to supply adequate building heat in cold climates.
What about the heat pump? This uses the same basic technology as refrigeration, but is able to reverse the flow of heat into and out of a building. “Heat pump” most often refers to an air-source heat pump (ASHP), because it exchanges heat with the air. When it’s very hot outside the ASHP is inefficient in expelling warm indoor air into an even hotter outdoors. Conversely, when it’s cold it is not efficient in pulling in heat from even colder outside air.
Heating with an ASHP is safe because there is no fire, but it’s barely a renewable technology. This is because it is difficult to contain heat in the air due to wind and changing weather patterns. It is, however, far superior to the most common type of electrical heating—electrical resistance. This is both inefficient and very expensive to use.
Once we begin to abandon heating by fire, heat pump technology becomes inevitable, with the more efficient heat pumps rising to dominance. This appears clear when one studies US DOE reports on the prospects for new technology in the residential (http://www1.eere.energy.gov/buildings/pdfs/residential_hvac_research_opportunities.pdf) and commercial (http://apps1.eere.energy.gov/buildings/publications/pdfs/corporate/savings_potential_comm_hvac.pdf) HVAC systems. Every potential future source of heating and cooling is some kind of heat pump.
Is there a
- renewable technology that
- uses electricity
- efficiently to heating indoor spaces?