Hybridization of solar PV and geothermal.

geothermal energy

Both geothermal power and solar Photovoltaics (PV) are renewable sources of energy, although geothermal unlike solar and wind energy is not intermittent and hence can be used as a base load power just like other conventional sources of energy powers like large hydro or diesel power generators.

Geothermal energy is a type of renewable energy which is generated within the earth and can be used directly for heating or transformed into electricity.  Geothermal power comes in three ways or power plants, that is, dry steam, flash and binary depending on how the hot water is cooled either under high pressure/low pressure to cool it (Flash) or when the hot water is passed through a secondary liquid with a low boiling point to turn it into vapor to drive the turbine. With dry steam power plants, the steam from the ground is used directly to drive the turbine while producing electricity.

Despite, the technology employed to drive the turbine and produce electricity, geothermal is site specific and not all places in the earth are endowed with geothermal resources. However, according to IRENA, geothermal energy can be sourced virtually everywhere although the vast majority of geothermal resources of economic value that are suitable for power generation are located to close areas of volcanic activity – for example, situated along plate boundaries (majority of the pacific), mid-oceanic ridges (such as Iceland and the Azores) and the rift valleys (such as the East African Rift) or near hot spots (such as in Hawaii).

Currently, about 20 countries use geothermal energy with the United States being the largest producer of geothermal in world and with the largest geothermal field. However, Geothermal energy is more prevalent in Iceland which has about 600 hot springs and 200 volcanoes and producing about 25% of its energy from geothermal power. Other countries that are endowed with a great resource of geothermal energy resources include Kenya, New Zealand, Philippines, Indonesia, Japan, Mexico, Italy etc

Solar PV integration with Geothermal Energy

Hybridization of renewable energy technologies is one way of solving, especially the intermittent nature of solar or wind power. In addition to use of artificial intelligence and machine learning to solve grid stability issues for utility scale solar and wind generation, using base load renewable energy systems such as geothermal instead of conventional power sources such as large-hydro and fossil fuels is one way of stabilizing the grid while decarbonizing it at the same time.

Countries rich in the geothermal resource including USA, Kenya, New Zealand, Iceland, Philippines etc, have benefited from this renewable resource while using it as a base load because of its constant and clean power available in all seasons.

However, depending on the geothermal technology employed (i.e. dry steam, flash or binary), the geothermal power plant output can be affected by the increased ambient temperatures during hot summer temperatures as noted by (DiMarzio et al. 2015). DiMarzio et al. 2015 captured one of the first ever geothermal plant in the world to integrate geothermal, solar photovoltaic and solar thermal for the Stillwater geothermal project which is located in Nevada, USA, and owned and operated by Enel Green Power North America, Inc. (EGP-NA).

power grid

DiMarzio et al. 2015 notes that the first phase of the project began with a geothermal plant, a 33 MW gross binary plant which was commissioned in 2009 and later in 2012 an additional 26MW of solar photovoltaic (PV) power was added to increase the output tailored to complement the geothermal plant output degradation during hot summer temperatures. During the hot summer seasons, the solar generated peak for the solar PV augments the capacity for the geothermal generated base load power increasing the power yield for the geothermal solar PV hybrid system.

However, every technology has its own limitations and when it comes to producing electricity from geothermal for example, the geothermal resource aspects such as temperature, pressure, flow or non-condensable gas content may change over time resulting in decreased power yields. Hybridization of geothermal with solar PV is a more cost effective option to mitigating this problem, because reworking the already depleting well may not be succesful while running a new well runs the risk of a dry or unproductive well (DiMarzio et al. 2015).

geothermal springs

When it comes to integrating solar PV with geothermal renewable resource for residential applications, this article captures some of the aspects of how solar PV and a geothermal heat pump can work in tandem to help regulate your home’s temperature using electricity provided by solar PV. Just like at utility scale, these two technologies even at residential scale can be complementary to help provide the power, heating and cooling for your home. For more details, how these two technologies complement each other at residential scale, check out this article.

Reference sources:

DiMarzio et al. 2015 : The Stillwater Triple Hybrid Power Plant: Integrating Geothermal, Solar Photovoltaic and Solar Thermal Power Generation, Proceedings World Geothermal Congress 2015, Melbourne, Australia, 19-25 April 2015.

Can solar panels meet your household heating needs?

energy efficiency

Solar Photovoltaic (PV) is a technology that works well to provide solar electricity suitable for running most of your electrical needs such as air conditioning, lighting, refrigeration, water pumping, etc. However, when it comes to thermal or heating needs, solar PV is not well suited. 

Solar PV can provide thermal energy, but it will require many solar panels than usual making it expensive.

For cost-effectiveness purposes, solar electricity (PV) is a great supplemental source of electricity and when connected to the grid, it can help to reduce your energy costs for on-grid PV systems.

For off-grid PV systems, hybrid solar PV systems such as solar PV /solar thermal with geothermal heat pumps, or with wind power systems or with solar power generators can offer solutions to meet all your energy solutions. 

Solar PV on its own can be an expensive energy option because you still need batteries to store excess power needed at night when there is no sunshine.

However, grid-connected PV systems can eliminate the battery cost. As such, during the day when your solar panels are generating power, it can be fed into the grid causing your meter to run backward helping to reduce your overall energy bill.

At night, this power can be drawn from the grid to power your household. At the end of the month, you can receive credit helping to reduce your energy bill. 

Technological options to supplement your solar PV for thermal or heating needs. 

During the day solar electricity can be used to run your air conditioning (in summer), refrigeration, lighting or water pumping for your pond, swimming pool, etc.

In winter, you might need to supplement your solar PV for heating or thermal needs. Thermal needs come in various forms, energy for cooking, energy for bath or energy for space heating, etc.

As such, the following energy options could be explored based on their cost, efficiency, and application:  

  1. Net metering: Grid-connected solar PV is a great solution to supplement your solar PV for the thermal energy needs that your system may not be able to meet. This is one option that is cost-effective and widely applied in many homes in the USA.  
  2. Geothermal Heat Pump for your home space heating or cooling: This is a renewable energy technology that has started to be applied for home space heating or cooling. It can be used to heat your home in winter and cool it during summer based on the fact that depending on latitude, ground temperatures range from 45°F (7°C) to 75°F (21°C).  As such, the geothermal heat pump takes advantage of this by exchanging heat with the earth through a ground heat exchanger since this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. However, this technology is still being developed and the cost might be prohibitive for some people, but with tax credits and other financial incentives from the government, it might work based on your budget and energy requirements. 
  3. All solar PV and solar thermal (heating): Rural areas that may be very far away from the utility grid might want to consider going all solar and using battery systems for storage to store excess energy produced during the day and using it at night. You might want to consider other renewable options such as geothermal energy or wind to supplement solar. All these options will depend on what technology is applicable in your situation and whether it is cost-effective or affordable.  Solar thermal (heating) in homes is mostly used to heat water used for showering, laundry, and other household use. 

All of the above options may or may not be feasible for your specific case and today with the advancement of software technology, you can use simple online tools like a solar panel cost calculator from the EnergySage to estimate for example, how many solar panels you need to power home and using their platform you can be guided when it comes to other energy options suitable for your specific case.