Why the Solar PV Industry Should Love Geothermal Heat Pumps Part 5


It’s a marriage made in heaven: Solar PV and Geothermal Heat Pumps

Part 5 of a 6-Part Series

The Green Marriage

In 2012, electric utilities saw solar panels as the “grave new threat” to operators of America’s electric grid because of the threat of falling revenues and declining customers (http://www.washingtonpost.com/national/health-science/utilities-sensing-threat-put-squeeze-on-booming-solar-roof-industry/2015/03/07/2d916f88-c1c9-11e4-ad5c-3b8ce89f1b89_story.html).

This is where the solar-GHP marriage comes in. Solar generates the electricity that the GHP needs to keep the building a comfortable temperature and to provide hot water.

The reason this alliance works so well is threefold:

  • Since GHPs run on electricity, the electric load on the house is higher, meaning the solar installer can sell more panels to cover the increased electric consumption.
  • GHPs consume more electricity in the winter. This builds load on the electric grid during off-peak times, evens out the seasonal variability in usage and increases system efficiency, all good for the electric utility.
  • Net Zero Energy (NZE) buildings are the latest housing trend. True NZE can be achieved by most homes only by a combination of GHP and PV technologies.

Many electric utilities require a load letter when planning the size of the PV array. The goal is to balance the home’s electric load with the electric production of the solar panels. When the load of the GHP system is added a larger array is needed, which increases PV sales volume.

Although the high efficiency of GHPs reduces peak load in the summer, GHPs also utilize electricity in the winter for heating, resulting in a higher yearly consumption. Of course, the elimination of the heating fuel bill more than offsets this increase.

GHPs augment PV’s smoothing of the demand curve and easing of peak load management. And by building load in the winter (increasing usage and sales when it was previously low) and reducing it in summer GHPs even out the seasonal demand and lower the peaks that keep rates high.

GHPs also increase system efficiency, which is desirable for the electric utility. The New York State Department of Public Service estimates that each 1% improvement in system efficiency (i.e. annual power plant capacity utilization) will yield from $221-$330 million in annual savings to ratepayers across the state. This is due to lower supply and delivery investment needs. This increased utilization makes it less likely utilities will need to institute surcharges for solar customers or increase rates for everyone.

In the end, the electric utility will be selling more electricity, at lower rates with the same profit margin. This can offset the loss in revenue that results from the widespread adoption of solar photovoltaic systems.

The Solar-GHP marriage is also the key to producing Net Zero Energy (NZE) buildings. A Net Zero Energy (NZE) building is one with zero net energy consumption. Its annual on-site electricity generation is about equal to the total amount needed for heating, cooling, hot water production and running appliances. New York State Energy Research and Development Authority (NYSERDA) has embraced NZE as its latest initiative. In NYS these houses will need GHPs to meet their heating loads and NZE requirements.


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Billii Roberti is co-owner, with her husband, of Green Choices Consulting. Together they researched energy efficiency, renewable energy and healthy building materials before renovating their home to ENERGY STAR® standards and included solar PV and geothermal heat pump system.

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