Electricity generation has always been to some extent a matter of combining the geography of resources with that of users. For example, coal-fired power stations were most often sited at the ‘mine mouth’, to minimise the transport of coal and instead transmit energy efficiently along high-voltage power lines. That also applies with the advent of large-scale renewables; getting the best out of wind and solar depends on siting plants where there is wind or solar resource.
Nuclear was to some extent an exception to this rule, as the energy in nuclear fuel is so large that the energy cost to transport it fades into insignificance, but that meant secondary resources, such as cooling water availability, came to the fore. Similarly, when a site meets renewables’ energy need – solar irradiation or high winds – it has a secondary resource need to meet: large areas of land. Again, nuclear’s huge energy resource means that it requires just a small footprint for power stations that export energy at very large scale. But in a twist of fate, many nuclear activities have been allocated extremely large land areas – whether that is for the more land-hungry activities associated with the fuel chain, for exclusion areas or simply as administrative areas around a power plant. These areas are generally off limits for the general public and excluded from other activities such as farming. But increasingly, they are proving attractive areas for installing renewable energy generation and in particular solar PV. The relatively simple installation and management of PV panels – and the speed at which the cost of buying and installing panels has fallen – has given rise to a ‘solar everywhere’ mindset and nuclear sites are no exception.
Solar offers nuclear the potential to increase income, reduce site costs or even help fulfil safety requirements.
Cleanup to Clean Energy
The US has seen an initiative that would produce solar energy at gigawatt-scale from US Federally owned nuclear sites.
The initiative is known as ‘Cleanup to Clean Energy’ and it was announced in July 2023 as part of the Biden-Harris Administration’s attempt to leveraging federal properties to support utility-scale clean energy projects. It follows Executive Order 14057, signed by President Biden in December 2021, which calls on federal agencies to achieve 100% clean electricity by 2030 and directs them to authorise use of their real property assets, including land for the development of new clean electricity generation and storage through leases, grants, permits, or other mechanisms.
The sites in question belong to the US government via the Department of Energy (DOE). Three of the DOE’s bodies, the Office of Environmental Management (OEM), Office of Nuclear Energy and National Nuclear Security Administration have joined together to identify about 35,000 acres (14,000 Ha) of land for potential development at five sites: Idaho National Laboratory (890 square miles, 2300 km2); Hanford in Washington; Savannah River in South Carolina (310 square miles, 800 km2); Nevada’s National Security Site; and the Waste Isolation Pilot Plant (WIPP) in New Mexico.
This could be just the first tranche: the DOE says once it has signed agreements on using the areas identified, a process expected to be complete this year, it will “continue to engage and partner with industry, tribal nations, communities, stakeholders, regulators and others to implement a process for further development of clean energy projects on DOE land”.
Four sets of leases have already been progressed by DOE:
At Idaho National Laboratory it will enter into lease negotiations with two developers. NorthRenew Energy Partners proposes PV on 2,000 acres (800 Ha) for a 300 MW solar farm, along with battery storage. Spitfire proposes to install a 100 MW solar farm on approximately 500 acres (200 Ha), again together with battery storage.
At Hanford, DOE will enter into negotiations with Hecate Energy, for a solar project capable of delivering up 1000 MW within an 8,000-acre (3200 Ha) area of the site.
At Savannah River, DOE has selected two potential projects. Stellar Renewable Power will enter lease negotiations for a 75 MW solar farm and battery on at least 500 acres (200 Ha) and Ameresco, Inc will be in negotiations for a 75 MW solar farm and battery on a further 500 acres (200 Ha).
At the Nevada National Security Site, Estuary Power LLC and NV Energy have been selected to begin negotiations over 2,400 acres (1000 Ha) for a solar farm of at least 200 MW.
Meanwhile at the Waste Isolation Pilot Plant a request for proposals has been extended and bidders will be named later this year.
Announcing bidders for the Hanford project, US Secretary of Energy Jennifer M. Granholm said: “With today’s announcement, DOE is transforming thousands of acres of land at our Hanford site into a thriving centre of carbon-free solar power generation, leading by example in cleaning up our environment and delivering new economic opportunities to local communities.”
Europe doubles land use
Legacy US nuclear sites have many thousands of acres available for alternative uses. That’s not the case at Europe’s compact nuclear power plants, but increasingly the ‘solar everywhere’ mindset has developers asking what areas can do ‘double duty’.
Rooftop PV has been increasingly commonplace over the last decade, but the advent of electric vehicles has made it an option for the ‘solar car park’.
The nuclear industry in the Czech Republic picked up this idea at an early stage. It was back in 2021 that power engineers completed construction of the country’s largest solar car park roof, at the Dukovany nuclear station. The CEZ group, which owns the plant, created 322 new parking spots covered by 2,600 photovoltaic panels. “Photovoltaics on the site of the Dukovany power plant is a very innovative concept. We believe that there will soon be many more such examples,” Minister of Industry and Trade Karel Havlíček said when it opened. “The new rooftop power plant at the parking lot in Dukovany is also a symbol of the future of the Czech energy sector – nuclear and solar zero-emission sources will be generating electricity here side by side,” said Daniel Beneš, Chairman of the Management Board and CEO of ČEZ. The solar car park includes three new public charging stations for EVs, adding to six existing at the site, with six more planned.
Dukovany’s array totals just 831 kW, but ‘solar everywhere’ assumes that large numbers of low power installations over large areas will provide bulk power (a contrast with nuclear’s small number of high-power installations, each with a small footprint). A law passed in France illustrates this: it requires any car park with 80 spaces or more to install solar PV covering at least half the site within five years from July 2023. Sites with more than 400 spaces have just three years to comply and France believes it could result in installations totalling 11 GW – significant in capacity terms, although of course it is only able to collect that much energy at peak periods on sunny days.
PV a positive for nuclear
These examples of solar installations focus on electricity production and scale, using the nuclear site footprint but operating separately. But in a recent paper published in Nuclear Analysis the authors (M. Chabook and S. Tashakor from Iran’s Islamic Azad University) investigate whether onsite PV and a battery could be used to increase safety at a nuclear plant.
In their paper, titled “Design of emergency solar energy system adjacent the nuclear power plant to prevent nuclear accidents and increase safety”, they said: “The main goal of this research is to use solar systems for providing emergency power to nuclear plants in case the power grid is down and other emergency systems such as diesel generators and batteries are not working”.
They modelled a relatively small-scale installation at the Tehran research reactor, a 5 MW pool-type light water research reactor that has been operating at the Tehran Nuclear Research Center since 1967. Emergency power at the Tehran research reactor for pumps, motors, light and all electrical equipment and labs is provided by a 450 kW diesel generator on the north side of the reactor building. This unit is backed up by a separate 62.5 kVA/50 kW diesel generator.
The authors say PV and a battery could back up the 50 kW generator (in case it failed or fuel was unavailable) and supply electricity to water pumps until the reactor’s other power systems are recovered. Iran is an ideal location for such an installation. It has high solar irradiation, with typically 300 sunny days per year. In many areas in Iran PV receives 5.4–5.5 kWh/m2, far above the level (3.5 kWh/ m2) where international standards typically consider irradiation is sufficient to allow for economic use of solar PV. The study used standard software (PVsyst) designed for analysis and simulation of photovoltaic installations, which can simulate the performance of solar in each country, city and zone. They used a second standard software tool (RETScreen Clean Energy Management Software) developed by the Government of Canada that allows for assessment and optimisation of the technical and financial viability of renewable energy, energy efficiency and cogeneration projects.
The research team considered the option of installing a 100 kW grid-connected PV system, which would require an area of 627 m2 of area, linked to a 400 kWh battery. The battery system can provide the necessary emergency power of 50 kW for eight hours. The model solar plant is intended to back up the 50 kW generator, which supplies electricity to the nuclear plant’s water pumps in case of emergency but the authors decided to model a larger array so that it also had more opportunity to export power to the grid (it also used novel inverters that allow for connection both to the grid and to battery packs). “As the first priority, the plant charges the battery pack and discharges excess energy to the power grid,” the authors explained, adding: “The system is capable of both charging battery bank and transferring excess energy to the grid, simultaneously.”
The paper concludes that the 100 kW solar power plant, connected to the grid, leads to improved back up capabilities at the Tehran research reactor. The system as designed could also generate revenue by selling surplus electricity to the electricity grid as when backup power is not required any excess generated energy is transferred to the power grid, with an associated income for the operator.
In an economic evaluation, the authors said 16,500 million Rials (US$390,000) was required for construction of the plant and annual maintenance cost would be 210 million Rials (US$5000). Economic evaluations suggested that the project could pay off its capital investment after 4.5 years, as long as exported power was able to access Iran’s solar feed-in tariff.
These types of exploration of the opportunities of other forms of generation on nuclear sites hints at potential new revenue lines for nuclear operators elsewhere.
Such revenue lines may be public-facing: EV chargers like those linked to PV – as well as nuclear – at Dukovany offer carbon-free power direct to EV drivers. But operators may also offer more specialist services to the power industry: together with the energy (and inertia) traditionally provided by nuclear, products like flexibility and fast frequency response are increasingly valued in the modern electricity market.
Alongside the bulk of a nuclear station, arrays of batteries may become increasingly common – and PV may be everywhere.
