Concentrated solar power (CSP) systems such as the FOCUS provide a highly efficient method of displacing emissions from the otherwise hard-to-decarbonize industrial heat sector, which accounts for almost 25% of global energy consumption (1). Indeed, one acre of land devoted to hosting FOCUS parabolic dish concentrators can provide CO2 mitigation equal to the CO2 sequestration impact of hundreds, or even thousands of acres of forest. This is in no way to discourage or disparage forest as a means for CO2 sequestration, since aside from that significant benefit it provides a multitude of other advantages, including supporting biodiversity, regulating the climate, and supporting forest-dependent populations. However, the comparison does highlight the unique and very significant impact that CSP systems such as the FOCUS can play in mitigating the accumulation of CO2 in the Earth’s atmosphere.
Concentrations of CO2 in the atmosphere now exceed 420 parts per million (2), levels not seen since distant human ancestor Australopithecus Afarensis walked the earth during the Pliocene, three million years ago. At that time, global average temperatures were 2-3 degrees Celsius higher than today (3), while global average sea levels are believed to have been 25 meters higher (4). And the pace of CO2 accumulation has been accelerating rapidly. In just over 250 years, atmospheric CO2 concentrations have increased by over 50% – with the majority of that increase happening in just the last 50 years (5).
As is widely known, this increase is due almost entirely to the CO2 emissions resulting from the combustion of coal, oil, and natural gas for energy. Indeed, of the 34.8 gigatons of CO2 emissions from fossil fuels in 2020, 14.0 gigatons came from coal burning, 11.1 gigatons from burning oil, and 7.4 gigatons from natural gas (6). So, to avoid the risk of an unprecedentedly rapid return to Pliocene climatic conditions, we must swiftly and dramatically reduce the CO2 emissions associated with combustion of fossil fuels and reduce the level of CO2 in the atmosphere.
Of the fossil fuels, coal emits the most CO2 per unit of heat energy generated (211 lbs/MMBtu), with natural gas the cleanest burning fuel (117 lbs/MMBTu) (7). The bulk of coal consumption is for electricity generation, while oil is primarily used to produce gasoline (156lbs/MMBtu) for transportation, as well as for industrial uses. Natural gas has been increasingly used for electricity generation, as a cleaner alternative to coal, but the largest single user remains industry, for industrial process heat applications.
Globally, industrial process heat accounts for over 25% of global energy consumption, according to the IEA (7). According to IRENA, 40% of industrial primary energy consumption comes from natural gas, and 41% from petroleum (gasoline) (8). In the United States, similarly, approximately 23% of all U.S. energy consumed is for industrial process heat. This thermal footprint is difficult to decarbonize, with heat being poorly suited large-scale central generation, and significant capital invested in the current industrial process heat infrastructure. However, CSP presents a potentially compelling option that could seamlessly integrate with the existing industrial process heat infrastructure. Indeed, NREL estimates that up to 25% of this industrial energy consumption, which equates to up to 6% of all U.S. energy consumption, could be met using solar thermal energy (9).
In addition to being a practical means of reducing CO2 emissions from industry, adoption of CSP can also be a hugely efficient method of decarbonization. A single acre devoted to hosting CSP systems such as the FOCUS parabolic dish concentrator can have an annual CO2 displacement impact equal to the CO2 sequestration of hundreds or even thousands of acres of forest. This is displayed in Table 1 below, which shows the acres of forest required to sequester the annual CO2 emissions avoided by one acre of FOCUS concentrators, at various DNI levels, for various fossil fuels displaced.
Table 1. Acres of forest required to sequester annual CO2 emissions avoided by one acre of FOCUS concentrators. (10)
The point is well illustrated in the below diagram, which shows the acres of forest required to sequester the annual CO2 emissions avoided by one acre of FOCUS units in a region with DNI of 5.00 kWh/m2/day, where the solar thermal energy is used to displace natural gas.
Diagram 1. One acre of FOCUS concentrators = 646 acres of forest (in annual CO2 avoidance terms).
Clearly, in higher DNI areas, or for dirtier fuels, the displacement impact of the FOCUS will be even higher. For instance, in Riverside, California, DNI approaches 7.00 kWh/m2/day, one acre of FOCUS units displacing propane, often used in rural settings, could result in a CO2 avoidance impact equal to over 1,000 acres of forest.
In addition to CO2 sequestration, there are many reasons to love forests. Forests are home to more than half of the world’s land-based species of animals, plants and insects. They regulate ecosystems, and buffer the impacts of storms and floods. By feeding our rivers, forests supply drinking water for nearly half of the world’s largest cities. They also provide shelter, jobs and security for forest-dependent populations, representing around 25% of the global population (11). Hence, protecting and restoring forests can provide enormous benefits to both humans and the wider ecosystem.
However, it’s important to consider the potential of technologies such as CSP, and particularly space-efficient systems such as the FOCUS, given their potential for disproportionately high CO2 avoidance impact and the urgency of reducing CO2 emissions.
"Heat is the world’s largest energy end use, accounting for almost half of global final energy consumption in 2021, significantly more than electricity (20%) and transport (30%). Industrial processes are responsible for 51% of the energy consumed for heat, while another 46% is consumed in buildings for space and water heating, and, to a lesser extent, cooking" – IEA, Renewables 2021 https://www.iea.org/reports/renewables-2021/renewable-heat
CO2 concentrations were 420ppm as of June 2022. https://keelingcurve.ucsd.edu/
“The Mid-Pliocene is the most recent period with atmospheric CO2 comparable with the present (ca. 400 ppmv) (24), with mean annual surface temperatures approximately 1.8 °C to 3.6 °C warmer than preindustrial temperatures, reduced ice sheet extents, and increased sea levels” https://www.pnas.org/doi/10.1073/pnas.1809600115
“Sea levels were estimated to be 25m higher than present day” https://www.usgs.gov/publications/pliocene-climate
Our World in Data. Emissions by fuel type: https://ourworldindata.org/emissions-by-fuel
Our World in Data. Atmospheric concentrations: https://ourworldindata.org/atmospheric-concentrations
EIA “Carbon Dioxide Emissions Coefficients” https://www.eia.gov/environment/emissions/co2_vol_mass.php
“Globally, industrial process heat accounts for more than two-thirds of total energy consumption in industry, and half of this process heat demand is low- to medium-temperatures (< 400°C). Currently, approximately 40% of industrial primary energy consumption is covered by natural gas and approximately 41% by petroleum. This means that there is a technical potential to provide around 15 EJ of solar thermal heat by 2030 (around 10% of industrial energy demand) while the share of solar thermal deployed in the industrial sector could reach 33% (IRENA, 2014a).” – IRENA
One acre can accommodate 70 FOCUS concentrators in a staggered array at 8 meter mast-to-mast spacing. Assuming 70% solar-to-thermal efficiency and 20% field/other losses, annual energy collected can be estimated as a function of DNI, in MMBtu. Using the EIA’s “Carbon Dioxide Emissions Coefficients” (https://www.eia.gov/environment/emissions/co2_vol_mass.php), the CO2 emissions per MMBtu of heat energy generated via combustion can be obtained. Thus, using the estimated MMBtu of fuel displaced by the FOCUS CSP field output, the CO2 emissions (metric tons) avoided by displacing each fossil fuel type listed in the Table 1 can be calculated. Using the EPA’s GHG equivalencies calculator (https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator), the acres of forest required to achieve an equivalent CO2 sequestration impact can be calculated. Per the EPA, one acre of forest sequesters 1.18 metric tons of CO2.
UN Environment Program – why do forests matter? https://www.unep.org/explore-topics/forests/why-do-forests-matter and IUCN Forests and Climate Change https://www.iucn.org/resources/issues-briefs/forests-and-climate-change