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Hybridization of wind farms: an opportunity for the sector

08 March 2021
Article by Bruno Silva and Miguel Marques and José Carlos Matos, members of INEGI's wind energy consulting team

Renewable energy sources are today an unquestionable part in the definition of energy policy, which ranges from macro planning, at national and community level, to the domestic level.

When we talk about electricity, specifically, the importance of exploring the diversity, and possible complementarity, of different renewable resources is increasingly evident. Full diversity ensures a balance, in terms of sources, in the production of electricity which, on the one hand, does not accentuate dependencies on specific sources or geographic regions and, on the other hand, maximizes the use of transport and distribution infrastructure without, however, the overload.

The vision of the operationalization of this diversification of sources, currently, involves the construction and operation of specific plants - the wind farm, the photovoltaic plant, the small hydro plant. However, the increase in power of existing electric power plants, with complementary technologies, can be an interesting opportunity for the National Electric System and all its stakeholders, from production to consumption.

Solar energy and wind energy, in particular, have characteristics that, depending on the intraday and intranual cycles, enhance their complementarity, and may have advantages in comparison to their individual and separate use. Let's see why.

The wind-photovoltaic energy potential

Each renewable energy source, whether wind, solar, water or biomass, has a different generation profile. There are variations over time, in geographic space, and in terms of availability and intensity.

There are, however, places that, due to their own meteorological conditions, allow a greater degree of complementarity.

Consider the example of places where there is more wind at night, than in places where there is more wind during the day. Here, the complementarity between wind and photovoltaic production would make it possible to boost energy generation with less volatility for 24 hours, making the most of each natural resource. A greater degree of complementarity allows for a greater smoothing of the generation profile of a hybrid power plant.

Hybridization, understood here as the combination of different resources, is not limited to the potential for smoothing the electricity generation profile. It also allows extracting more value from an asset with a potential limited to the productivity associated with the plant's technology: the grid connection infrastructure itself.

Capacity, location and intraday cycles are key factors

Wind farms in Portugal have an average productivity of 2300 to 2400 hours equivalent to full load. The connection of these farms to the network has, of course, the same degree of use, which in turn means that more kWh delivered to the network by this route results in the use of the idle capacity of this asset. In other words, if the cost of producing additional electricity requires additional investment, the cost of delivering that electricity to the grid is residual, since that delivery is made through an existing asset. Something that ultimately results in a reduction in electricity costs.

And why is this question posed to wind farms?

From a conceptual point of view, the hybridization hypothesis can be placed for any power plant. However, in view of the dimension supported by wind energy in the National Electric System, the opportunity is more obvious here.

Let us remember that, in mainland Portugal, in the last 5 years, electricity from wind sources corresponded, on average, to 24% of electricity consumption.

In addition to the level of intensity of the wind and solar sources, however, it is necessary to verify the degree of complementarity between the two, project by project. A high simultaneity of resources can have a significant impact in terms of the limitation imposed on the hybrid power plant, assuming the lack of storage.

Measuring the cycles, both intraday and interannual, of electricity production from different sources, and determining the greater the degree of desynchronization (i.e., the lesser the degree of simultaneity) is equally important for the best dimensioning of the photovoltaic plant.

Thus, we conclude that one of the main inputs for the definition of the optimum point in the exploration of a hybrid plant is found in the degree of complementarity between capacity factors. However, this is not the only relevant aspect: location is also a key aspect, and depends on several factors, including the characteristics of the surrounding terrain, the classification of the soil and the existing resource levels.

Renewable electricity generation capacity has room to grow in Portugal

These studies thus prove to be an essential step towards the future success of a hybrid plant, and INEGI also has the knowledge and skills to carry them out.

In studies already underway, our team uses advanced methodologies to measure the simultaneity of the sources and to evaluate the surrounding terrain, which allows us to equate the levels of incident solar irradiation, the orographic characteristics of the terrain (orientation, inclination, etc.) constructive solutions to classify and pre-select the areas of greatest interest, in view of the basic criteria, in addition to local verification and assessment of environmental aspects.

The hybridization of wind farms, using the photovoltaic generating capacity, is a very interesting opportunity for the first promoters to invest in this bet in Portugal. Given the typical productivity of the parks in the country, it is expected that there will be significant idle capacity on the part of the grid connection infrastructures, which can be used with renewable sources as long as they are out of sync with wind energy.

In a work that INEGI has been carrying out for more and more developers, the photovoltaic plant added to the wind farm can be optimized according to the potential and its characteristics, aiming to maximize electricity production for the whole year or just for a specific period of the year if, in the overall balance of the hybrid plant, this proves to be more interesting.

In any case, this is just one aspect to be considered in studies to increase the power of wind farms with photovoltaic generation. The potential replacement of wind turbines with more efficient machines, the so-called repowering, the conclusion of periods with administratively determined tariffs, and the entry of wind farms into the market or any profound changes in the profile of electricity demand can lead to profound changes in business models.

Read the full version of this article, HERE.

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