Oxford PV                            OSE0047

Written evidence submitted by Oxford PV

Oxford PV welcomes the opportunity to respond to the Environmental Audit Committee’s Technological Innovations and Climate Change: Onshore Solar Energy Technologies call for evidence.

Oxford PV is a pioneer and recognised leader in the field of perovskite photovoltaic (PV) technology. The company is a 2010 spin-out from the University of Oxford. The Oxford PV R&D Headquarters are based in Oxford (UK), while the pilot and manufacturing line is in Brandenburg an der Havel, just west of Berlin (DE). Perovskite PV technology provides superior performance compared to standard silicon PV with a lower cost of generated energy and reduced environmental footprint. Oxford PV is expecting to have commercially available cells in 2023.

UK Energy security can only be achieved by relying on faster deployment of affordable renewable energy sources, and solar energy is the best technology for this energy transition. Oxford PV believes that the UK has a genuine opportunity to become a leader in the manufacturing and commercialisation of innovative high efficiency and sustainable PV technologies. The Oxford PV feedback is based on over 10 years of experience in the perovskite PV field.

We have provided a general overview of the PV landscape from a technological perspective, and afterwards, responses to three of the proposed questions, focusing on developments in solar panel technology, material sustainability, and supply chain resilience.

General overview of the PV landscape

There are two mainstream PV systems in the market, wafer-based and thin film PV. In the former, solar cells are manufactured in bulk, as is the case of silicon, which means that the module is made by the interconnection of individual cells; these are the panels that are generally seen on rooftops. In the decades since the first commercial silicon cell was made in 1954, crystalline silicon technology has undergone substantial technological development, and is 95% of the PV market. However, silicon is nearing its practical power conversion efficiency limit around 26%, which restricts its prospects for further cost reduction and power output improvements beyond the short term.

Although silicon is currently the mainstream technology, it has the disadvantage of being a poor light absorber. To fully absorb the useable sunlight and to ensure mechanical strength, silicon cells are about 200 microns thick. In contrast, the second type of system, thin film PV, uses more efficient light absorbing materials, which allows them to be processed into films that are about 100 times thinner than silicon. This property leads to lower material consumption and therefore a more efficient use of resources. Thin-film PV makes up the majority of the remaining 5% market, and the main technologies are cadmium telluride (CdTe) and copper indium gallium selenide (CIGS), which can be processed with less energy intensive methods than crystalline silicon, but rely on scarce or expensive elements such as tellurium, indium, and gallium.

In general, any photovoltaic solar semiconductor material has a theoretical efficiency limit of 29-33%, but they are limited to around 26% in practice due to unavoidable losses. To overcome this practical limitation, multiple solar cells can be stacked together to form multijunction systems that make more efficient use of sunlight by having each sub-cell targeting a different spectral region. Triple-junction compound semiconductor solar cells that reach efficiencies around 40% are routinely used for space applications, but their high manufacturing cost and use of scarce materials, such as gallium, eliminate them for broad terrestrial use. Industry roadmaps for photovoltaics such as the International Technology Roadmap for Photovoltaic (ITRPV)[1] predict the incorporation of tandem systems in the market by 2024 (the simplest multijunction embodiment that uses only two junctions).

To have a proper overview of the PV landscape and where the industry is headed, it is necessary to consider a highly promising emerging thin film PV technology called perovskite. The perovskite material usefulness in photovoltaics was first recognised 13 years ago and has already achieved efficiencies on par with the best available silicon cells in only a fraction of the development time. The perovskite absorber material is comprised of abundant elements that are readily available from primary sources and can be manufactured using energy efficient and low-cost processes. Furthermore, the perovskite optical properties can also be adjusted to complement other solar absorbers, including silicon, for use in multijunction designs. By virtue of being a highly efficient and tuneable solar absorber that can be processed at scale with low-cost and available resources, perovskite PV is an ideal technology for commercialising next generation modules using tandem cell technology capable of yielding substantial efficiency gains over silicon. Oxford PV is about to introduce a perovskite-on-silicon tandem cell, with a market entry cell efficiency of 27%, while maintaining affordability and competitiveness in the market[2].

What role can developments in solar panel technology play in the UK’s transition to net zero?

Efficiency and lifetime are the metrics used to compare solar panels and thus, assess new developments. Standard silicon solar panels have an average efficiency of 20%, with the highest commercially available panel at 22.8%. Most of the solar module suppliers offer guarantees for 25-30 years.

Silicon solar panels are usually made of 60 or 72 interconnected solar cells, and the efficiency of a solar panel is fundamentally determined by the efficiency of the solar cells within the panel. Silicon solar cells have an average efficiency of 22%-23%, new generations of silicon technologies are achieving over 26% and therefore their practical limit as discussed in the first section.

The importance of efficiency in solar panels.

High efficiency solar panels produce more energy in the same space, or in other words, the same amount of energy can be produced in less space. This addresses extended land usage and space-constrained locations challenges, such as residential areas. As an example of high efficiency developments, the first generation of perovskite-on-silicon tandem modules will generate 20% more power than standard solar panels; 20% more power in the same space.

The “lack of sun” in the UK is generally raised as a concern for the deployment of solar. It is a reality that the number of sunshine hours in the UK is lower than in southern European countries. i.e. Considering an average of 30 years, Manchester (UK) has 50% less hours of sun than Madrid (Spain)[3]. It is another reality that in cloudy days the sun still shines, even if the irradiance is lower. An average decrease of 80% on the power output of modules in a cloudy day versus the optimum has been estimated by several sources, therefore, access to high efficiency technologies will balance some of the losses due to lower irradiances and become more relevant for less sunny geographies such as UK. In particular, high efficiency perovskite-on-silicon tandems can behave differently at low irradiances and lose less of their power output on cloudy days than traditional silicon based solar cells.

Innovation

The UK has a thriving community involved in many of the breakthrough innovations that will help the country and the world to deploy solar energy faster and better.[4] This community is dispersed and diverse, but it provides the UK with a strong base to convert its technology leadership into competitive advantage that is conducive to commercial and industrial success. As new technologies will be crucial for accelerating solar energy, strengthening the UK’s ability to innovate in solar PV will help the country to sustain a robust talent pipeline, to develop its industry, and to transition to net zero in the long run.

The UK is holding the leadership role in the innovation and development on the next PV generation, perovskite PV. The technology was discovered by Prof. Henry Snaith, University of Oxford, and taken from lab to commercialisation by Oxford PV. The UK is in an excellent position to develop the next generation of solar, becoming a manufacturing leader. The potential of this technology is established by the continuous world-records perovskite-on-silicon tandem cells are achieving, with 31.3% at lab scale[5] and 26.8% at M6 wafer size by Oxford PV[6].

How sustainable is the supply chain for solar panel manufacture? Do levels of sustainability differ between mature and emergent technologies?

Photovoltaics do not generate any greenhouse gases during operation, the largest contributor to their carbon footprint is the primary energy sources embodied in their production, which varies between different technologies. Silicon solar carbon footprint is relatively high due to the energy intensive process use to grow high purity solar grade ingots, which accounts for 90% of the total energy used. In comparison, thin-film PV panels carry less than half the carbon footprint and have a water footprint three times lower. Thin-film PV is also advantageous in terms of circularity, up to 90% of materials is recovered at the solar panels’ end of life[7], in comparison with the average 80% on standard silicon.

Sustainability in emerging vs mature technologies

High efficiency technologies, such as perovskite-on-silicon tandem, have a lower environmental impact as the additional energy generated considering similar lifetimes, balances the extra manufacturing steps and materials required.[8]

The demand for raw materials for the production of solar panels is expected to increase exponentially as we transition to clean energy systems[9], therefore a determining factor will be the use of technologies manufactured with abundant and readily available materials. Such technologies already exist, as silicon or the emerging perovskite PV. In a scenario where 14TW of solar, required to meet net zero goals, would have to be deployed with perovskite-on-silicon tandem. The total of the raw materials could be mined in less than 5 years.[10]

Does the concentrated global distribution of solar panel supply chains (80% manufacture in China) pose a risk to solar technology expansion in the UK? If so, how could this be mitigated?

The supply chain for silicon solar manufacturing is almost concentrated in a single country. In 2021 China held 72% of the world’s polysilicon capacity, 98% of solar ingots, 97% of solar wafers, 81% of solar cells, and 77% of solar modules. Within China, the majority of PV production is further concentrated in the provinces of Xinjiang and Jiangsu, according to a recent report on Solar PV Global Supply Chains by the International Energy Agency.

UK should not depend on third countries to meet its energetic requirements, and focus on enhancing its manufacturing capacity and creating partnerships with allies to achieve a more geographically localised supply chain. In addition, as mentioned in a previous question, UK is very well placed to take on more innovative technologies and support their commercialisation by removing bottlenecks on funding acquisition, access to land and permits expedition.

Human rights

The region of Xinjiang, where the majority of the silicon solar manufacturing is located, was recently reported for the use of forced labour. The rollout of renewable energy must never come at the expense of human rights, and the UK must ensure a clean and transparent supply chain. The UK should consider regulations similar to the US Uyghur Forced Labour Prevention Act (UFLPA) or the EU forced labour ban proposal.

In summary, Oxford PV fully support all initiatives targeting an increase on solar deployment, making solar the driver of the energy transition. We remain available if further input is required.

December 2022