They say there’s nothing new under the sun. Don’t believe it. Innovation is full speed ahead in the solar energy photovoltaics (PV) sector to create more efficient and cost-effective solar panels, with new materials and modules for deployment on buildings, agrivoltaics and floating solar installations, as well as conventional installations worldwide. There is also an eye on improved sustainability, recycling and re-use.

Global installed solar PV capacity has climbed from 2 GW in 2002 to more than 1 TW in 2022 and is expected to increase substantially over the coming decades, according to the Global market outlook for solar power 2022–26, published by SolarPower Europe. What’s more, solar power is now 88% cheaper than forecast a decade ago.

There has also been competition to increase the efficiency of solar panels which have long been around 15–20%. Indeed, the first solar cell was invented by New York inventor Charles Fritts in 1883 by coating selenium with a thin layer of gold – sounds expensive! Then Bell Labs created the first practical silicon solar cell in 1954, with cells of about 6% efficiency.

Crystalline silicon has made tremendous advances since that time but is now nearing its practical limit. Search has been underway worldwide to secure more power from a solar cell. Most of the innovation has been around silicon cost reduction by automation and scale-up of manufacture productivity.  

Today China dominates the manufacture of PV solar cells and modules, accounting for 82% of production with other South East Asian countries accounting for a 14% share, according to Rystad Energy’s Solar Supply Cube.

n-type versus p-type

Major suppliers and several new entrants have announced a significant expansion of module manufacturing capacity, focusing on n-type technology, which has a slightly higher efficiency than the current mainstream passive emitted rear contact PERC (p-type) technology, at a slightly higher cost.  

Technically, a p-type has a silicon wafer doped with boron, which has one less electron than silicon, making the cell positively charged. Whereas an n-type cell is doped with phosophorus, which has one more electron than silicon, making the cell negatively charged.

Perovskite initiative

At the turn of the new millennium, Professor Tsutomo Miyasaka of the Toin University of Yokohama discovered the use of perovskite for PV. A paper that he jointly published with Professor Henry Snaith of the University of Oxford and others in 2012 spurred the whole field of perovskite PV development.

In 2014, Oxford PV, a company co-founded by Professor Snaith refocused the company to develop an approach putting perovskite on silicon solar cells together to produce a more efficient ‘tandem’ solar cell. Each solar cell captures complementary parts of the solar spectrum, maximising the power generated from the combined cell.

In December 2020 Oxford PV achieved solar PV cell efficiency of 29.52%, a world record at the time. In July 2022, researchers at the Swiss Centre for Electronics and Microtechnology (CSEM) and the École Polytechnique Fédérale de Lausanne achieved a power conversion efficiency exceeding 30% for a 1 cm2 tandem perovskite-silicon solar cell, certified by the US National Renewable Energy Laboratory (NREL).

Oxford PV has brought a factory online for their tandem solar cell at Brandenburg near Berlin, which is currently being prepared for commercial manufacture as a multi-MW facility, due to begin commercial output in 2023.

Chris Case, Chief Technology Officer of Oxford PV, estimates there are about 20,000 scientist and engineers working on perovskite-solar technology round the world. He insists: ‘We love competition because it verifies and validates that what we’re working on makes sense. The good news is we have a leadership position in this product, with 530 patents as a first mover.’

Recycling and sustainable design

There is also an issue around the sustainable design of solar products, which is now being addressed.  

Oxford PV is among the many industry players supporting an initiative called Ecodesign aiming to establish a harmonised set of sustainability requirements and eco-labelling for the PV sector at EU level, initiated by the European Commission. Proposals for strong Ecodesign policies for solar products (including solar panels) are backed by a number of industry associations including SolarPower Europe, PVthin, the European Solar Manufacturing Council, ETIP-PV and the IECRE.

Solar PV recycling is already mandatory in the EU, which caters for up to 90% of the weight of the component’s materials.  

‘Nine out of 10 people across the EU indicate solar as their preferred energy source to affordably address climate change and help the EU decarbonise.’ – SolarPower Europe

Solar market projection

Solar PV is a very large and innovative industry with accelerated technology development driven by the UN Paris Agreement which aims to keep global temperature rise to 1.5°C. Indeed, a European Commission report to the European Parliament and Council on the ‘Progress and competitiveness of clean energy technologies’, published in October  2021 claimed: ‘This technology is central to future climate neutral electricity generation systems.’  

The report forecasts that over 3.1 TW of PV capacity is projected to be installed globally in 2030 and about 14 TW in 2050. Investment required between 2020 and 2050 for additional solar power capacity is estimated to be about $4.2tn. About 0.4 TW of solar PV capacity is projected to be installed in the EU by 2030, compared to 160 GW in 2021, with 1 TW by 2050, according to the International Energy Agency's (IEA) Sustainable Development Scenario.

However, the EU has slipped to third place after Japan and Korea in terms of high value solar electricity inventories (generation), and China will soon surpass the EU in this respect, based on Joint Research Centre and EPO Patstat estimates. Nevertheless, the EU remains a global leader in several parts of the PV value chain, in terms of R&D, polysilicon production equipment and machinery for PV manufacturing.

‘PV systems tend to be increasingly complex, requiring further investments to remain at the cutting edge,’ states the EC report.

Here are some interesting initiatives.

Agrivoltaics

Several companies in Europe are developing solar technology to cover a variety of crops from wheat fields and vegetables to fruit orchards. The solar panels help insulate ground beneath the solar panels by around 2°C, protecting the crops and vines from late frost and generating enough power to power several hundred homes. Typically, farmers give priority to crop quality over power production, so 15–20% of potential energy supply is lost over the course of a year.

For example, a roof of solar panels, supplied by Lyon-based Sun’Agri, at a French vineyard in Perpignan, insulates the grapes during periods of extreme cold. The panels rotate to allow more sunlight to hit the vines on more overcast days.

BayWa re’s Dutch subsidiary Groenleven has developed a pilot project with research institute Sint Oedenrode at Hoof in the Netherlands, with 500 installed modules as an agri-pv test installation for raspberries and blackberries.

Floating solar – floatovoltaics

Akuo Industries also manufactures the Hydrelio floating PV structure developed by French company Ciel and Terre International, which optimises the power plant by cooling the panels and preserving water resources by reducing evaporation. The Hydrelio floating technology consists of a modular HDPE assembly and is now installed in over 150 projects and on all types of reservoirs. The power plant is maintained in place by anchoring lines fixed on the bottom of the lake or on the banks.

BayWa re worked with Ubon Bioethanol, a supplier of processed cassava products, to set up a floating solar platform in Ubon Ratchathani, Thailand. The floating PV farm is expected to generate 4,440 MWh in its first year of operation.

Floating PV solar cells can offer a host of alternative locations for solar farms in reservoirs worldwide, like this BayWa re installation
Photo: BayWa re

Lightsourcebp built and installed Europe’s largest floating solar farm, supplying 6.3 MW at the Queen Elizabeth Reservoir in south-west London in 2016, which is connected directly into Thames Water’s private network, supplying green electricity to the utility company via a power purchase agreement. However, company spokesperson John Parnell told New Energy World: ‘Floating solar is definitely not a priority for us. It’s not going to play a substantive role in the energy transition, even in Asia.’  

TOPCon modules

Lightsourcebp is now focused on utilising bifacial modules and new TOPCon modules to boost efficiencies. Its latest project will be the largest solar plant in the UK at Tiln Farm in Nottinghamshire with maximum output of 61 MW. The company claims to have 55 GW of solar projects in the pipeline.

TOPCon modules will compete with traditional PERC solar products, according to recent research by Germany’s Fraunhofer Institute. However, efficiency gains are necessary for TOPCon modules to capture market share, as production costs remain higher than those for PERC.

TOPCon stands for tunnel oxide passivated contacts. According to PV Magazine, the economic viability of TOPCon requires stable 24/7 production to create utilisation rates comparable to PERC cell manufacturing facilities. Additionally, TOPCon cells on an n-type substrate require silver contacts on both sides. Reduction of silver usage will be important for this concept to succeed in the mid to long-term.

Processes and equipment that are commonly used in the manufacture of PERC cells may be easily adapted to TOPCon cell production by adding two process steps, say the German researchers – the formation of tunnel oxide and the deposition of intrinsic/doped polysilicon.

Vertically mounted solar panels

Norwegian company OverEasy has introduced vertically mounted bifacial solar panels, which offer two energy production peaks, using solar panels facing in two directions. The company’s V-bifi solar panels have been installed in Bergen, Norway; York, UK; and Valencia, Spain.

OverEasy vertically mounted bifacial (V-bifi) solar panels at Tromso, Norway, can face in two directions to catch the sun
Photo: OverEasy

Solar energy can be used for heating or cooling. The challenge is to integrate more solar-driven technologies into buildings’ heating and cooling systems on the road to net zero emissions, at even lower cost with greater conversion efficiency.