Interest in co-locating wind and solar photovoltaic facilities is growing, but finding suitable sites can be a challenge. Strong wind and solar resources are just two of the ingredients needed to bring together a viable hybrid project and experts remain divided about the real potential of such an approach
“The beauty of wind-solar hybrids is that the wind tends to blow the hardest when the sun is not shining,” says Rahul Munjal, head of renewable energy firm Hero Future Energies in India. In April 2018 the company inaugurated the first large-scale wind and solar photovoltaic (PV) hybrid power plant in the country, where hopes for wind and solar hybrids are high. The facility is located in the state of Karnataka in southwest India and combines 50 megawatts (MW) of wind turbines with 28 MW of PV. Hero also plans to add storage to the project. That the variability in wind and solar output in some geographies is often, although not always, complementary goes a long way towards explaining the increasing interest in combining them in a single power project. Wind often tends to be strongest in the evening and early morning, when the sun is rising and setting, and the two resources also complement each other well on a seasonal basis. “Looking over the lifetime of a plant, you can balance the output of the two assets to get a firmer and more secure production profile,” insists Mads Blumensaat from Vestas, a Danish wind turbine manufacturer. Along with wind and solar irradiation, crucial to the hybrid investment case are cost synergies, namely for transmission infrastructure such as interconnections and substations. Developers also point to synergies in land use and permitting along with improvements in forecasting and scheduling power production that can bring down balancing costs. And while the two technologies are quite different, with operations and maintenance for wind farms decidedly more complex, they also see room for saving at least a little money in this area as well. From a cost perspective, there are no disadvantages from combining wind and solar assets, says Vicente Garcia Munoz from Siemens Gamesa, a Spanish renewables company. As is the case with standalone wind and solar farms, hybrids will not be built if there is not a business case, he adds.
You already need the stars to align to have an optimal wind site,” says Michael Goggin in the US, vice president of Grid Strategies, a consultancy. “And it becomes even more complicated when you add solar to the picture.
Location, location, location
Despite the potential advantages of hybrid power stations, there is one major catch. Finding the right location can be a challenge. “You already need the stars to align to have an optimal wind site,” says Michael Goggin in the US, vice president of Grid Strategies, a consultancy. “And it becomes even more complicated when you add solar to the picture.” Finding sufficiently strong wind and solar resources that are complementary at a specific site is not easy, but it is not the only condition for a hybrid project. “The development of wind and solar hybrids depends on the availability of resources, land and a regulatory framework that allows adequate remuneration for investors through power purchase agreements,” says Giovanni Tula, head of innovation and sustainability at Enel Green Power. The surface area required for a co-located wind and solar PV plant is less than the sum of its parts. At the same time, the larger land footprint of solar projects is one reason that not all wind farms with strong solar resources could be fitted with solar panels. Solar at times must compete with alternative land uses, such as farming and ranching, which thrive at many existing wind farms. For this reason, solar PV plants may also face difficulty securing land leases and approval from local authorities on sites already occupied by wind farms, particularly when land is scarce or alternative, less land-intensive green energy sources are available.
Regulatory constraints
Daniel Fraile, head of market intelligence at WindEurope, the European wind lobby organisation, highlights regulatory constraints that have impeded the development of wind-solar hybrids in Europe and further afield. Among these is pricing. “With feed-in tariffs and feed-in premiums, you would choose either wind or solar. Imagine you get paid €40 a MWh for solar and €30 a MWh for wind, how much do you get for output from the hybrid plant and how do you differentiate between them? They may seem like simple questions, but they need to be resolved. The potential for wind-solar hybrids depends on the regulatory framework.” Garcia believes regulatory frameworks will increasingly adapt to make room for both hybrids and storage. “We expect these technologies to be considered more and more within political frameworks in the future,” he says. “At a certain percentage of renewable energy in the energy mix, these technologies will be needed to ensure grid stability.” Market players agree that one factor that can help tip the balance in favour of wind-solar hybrids is the grid. “If there are constraints in terms of the interconnection process and high grid connection costs, then these projects can be more economically attractive,” says Goggin. Indeed, hybrid power facilities, increasingly wind and solar, are not a novel solution for serving micro-grids, or isolated communities in sore need of electricity, such as those on small islands. What is new, is that hybrid wind-solar projects are now being used for commercial-scale projects on the main grid.
Southern projects
One country where grid issues are seen as encouraging the development of larger wind-solar hybrids is Australia, where a few hybrid projects coming in at 1GW and upwards are already planned. Construction on the first 60.2 MW of the so-called Kennedy project, which could see its capacity built up to 1.2 GW, is now underway. “If you look at Australia, there are very long, low transmission lines that are quite vulnerable compared to the Danish grid, which has a much smaller grid with strong interconnections,” says Blumensaat. The state of the grid could also be one factor helping to encourage the growth of hybrid plants in India, whose government this year came out with a wind-solar hybrid policy. Munjal sees “huge potential” for wind and solar plants in India, where he says ten of the country’s 29 states boast good wind resources and strong solar irradiation resources are spread throughout the country. Hero’s inaugural hybrid plant began operations in a market lacking a clear policy on prices for hybrid power production. The company sidestepped the problem by selling power directly to industrial electricity consumers at mutually agreed prices. And, in June, the government’s Solar Energy Corporation of India (SECI) sought to help make the market framework clearer at a national level by issuing a tender for up to 2.5 GW of wind-solar interstate transmission system connected hybrids at a maximum price of INR 2.93/kWh (€0.04/kWh). According to the terms of the tender, the SECI will purchase power from successful bidders for a period of 25 years. Brazil got its first wind-solar hybrid in 2015, when Enel Green Power combined two solar facilities totalling 11 MW with an existing 80 MW wind farm. Empresa de Pesquisa Energética (EPE), the country’s federal energy planning company, made a qualitative assessment in 2017 of hybrid solar-power facilities and the power regulator is set to begin evaluating the regulatory framework this year. In its analysis, EPE indicates that even in Brazilian regions with strong solar irradiation and wind, there may be major variations at a micro-climatic level and projects must be decided on a case-by-case basis.
Site specificity
Developers and technology providers alike agree with this view, stressing that the feasibility of wind-solar hybrids depends extensively on site-specific conditions. Site specificity, combined with the relative newness of wind-solar hybrids for large-scale projects and an uncertain regulatory framework in many places, means that solar-wind hybrid potential can be particularly hard to gauge. That said, many expect the importance of hybrid projects to grow and an increasing number of renewable energy power station developers are looking into the possibility. Among factors driving their interest is the competitive backdrop for renewable power producers. While the cost of energy production, levelised over the lifetime of a project, has declined significantly for both wind and solar PV over the years, so have the prices received for the power being sold. “When the integration of wind and solar assets results in a good level of savings, this can generate a higher return on the investment,” says Tula. “When” and “can” are the operative words in the sentence. Blumensaat expects the push for hybrid projects to accelerate with increased electrification as demands placed on the grid increase in step with the greater percentage of energy for heating and cooling and transport to be sourced from renewable power. “There are many ways to deal with grid and network issues, but if you can start to control output from a single site to a greater extent, this benefits everyone.” Along with continuous reduction in the levelised cost of energy from renewables, he sees hybrids contributing to renewable industry efforts to lower the levelised cost of balancing the power system. “The grid is the condition for our existence and we have to bring more to the table.” Goggin, on the other hand, is more cautious, forecasting that only on a relatively limited number of sites will it make sense to co-locate wind and solar plants. But he stresses that hybridisation gains may also come with two distinct wind and solar projects. “If you were to develop a wind farm and you find a site that is better for solar PV ten miles down the road, you won’t use the same interconnection but there will still be benefits from the higher use of the transmission line.” Even when wind-solar hybrids do not make sense, a hybrid approach could representative an attractive alternative.
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Heather O’Brian