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Solar roofs, a solution to reduce emissions and lower electricity bills

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    In April the United Nations (UN) sounded the alarm: the world needs to reduce its greenhouse gas (GHG) emissions by 43% by 2030 to comply with the 2015 Paris Agreement to limit global warming by 1.5° degrees by the end of the century. Although Chile only contributes 0.25% of total global emissions, it has seven of the nine climate change vulnerabilities, reflected in the megasequence and glacier melting.

    Chile was the first country to establish the 2050 decarbonization goal in a law - Framework Law on Climate Change - passed in March. Thermoelectric plants have already begun their plans to replace coal with renewable energies and companies and individuals in several countries, including Chile, are beginning to install solar plants on their roofs to generate their own energy at the place of consumption, reduce emissions and, incidentally, lower their electricity bills.

    "Decarbonization as a service

    For example, in the business sector, since 2010 Solarity has been installing solar plants on the rooftops - idle spaces - of the facilities of companies in sectors such as industrial, retail and agriculture. It offers "decarbonization as a service", where they pay for the investment of the plant in exchange for a long-term contract for the purchase of the energy generated at a lower price than the traditional market.

    Horacio Melo, founder of Solarity, says that in the first four years he had to "evangelize" rather than sell. But now he perceives a growing interest of companies to supply themselves with clean energies, which together with the drop in panel costs is pushing demand upwards. "The last plant cost us half as much as the first one we did six years ago," he says.

    He points out that the square meter (m2) of panels costs $60,000 and the cost of the infrastructure to produce one kilowatt (kw), ranges between US$800 and US$1,000. Although these numbers are going down, the limitations for their massification have to do with two factors: the space on the roofs to install the panels -which is finite- and the hours in which a company operates.

    He explains that the percentage of consumption that they manage to supply with solar roofs depends on how intensive the company is in energy use, but in general ranges between 10% for the food industry, between 30% to 50% for retail - where the highest consumption is in lights and air conditioning - and up to 60% in the agricultural industry "if you look at the whole year," he says.

    Melo says that the hours of sunshine and the operation of a company are also a limiting factor, because there are companies that operate 24 hours a day and the solar plant only generates the hours of sunshine. However, there is already a solution, the costs of batteries to store energy "are going down" and in fact, Solarity already has a pilot and a plant that operates with batteries.

    Regarding the impact, he says that the main ones are the drop in the cost of energy, the reduction in the generation of emissions and a reputational impact, because "customers are increasingly empowered and, my projection, is that in the future we will discriminate against companies that do not have a decarbonization plan".

    He explains that a 1MW plant, in 10 thousand m2 of roof, reduces 150 tons of carbon dioxide (Co2) per year, that is, "the C02 captured by 10 thousand trees per year".

    One of the companies that has a solar plant is Sodimac, of the Falabella holding company. In 2016, the chain of construction and home improvement stores entered into partnerships with Solarity and Efe Solar, a company that also provides renewable energy for companies.

    Sodimac's Sustainability Manager, Juan Carlos Corvalán, says that this technology has been implemented in 48 of its facilities, including stores, the head offices in Renca and the distribution center in Lo Espejo. The last branch where solar roofs were installed is in the city of Temuco on Los Pablos street.

    In relation to the impact, he indicates that they supply about 30% of the total consumption of the Sodimac facilities where they are implemented, the rest is obtained from the grid. "In 2021, we were able to inject up to 16 giga watt/hour by generating photovoltaic energy and managing to avoid the emission of more than six kilotonnes of CO2 or equivalent gases, which is equivalent to 2,630 houses of annual electricity consumption," says Corvalán.

    And the goal, he says, is "to supply all its stores and offices with clean energy by 2030".

    Regulation and incentives: Germany and Chile

    One of the most advanced countries in clean energy is Germany, where 32% of its energy matrix comes from renewable energies, according to government data as of 2016. For the same reason, it has also advanced in self-generation. The first regulation is the Renewable Energy Sources Act of 2000, which fixed the price of renewable energy sold to the grid.

    Christoph Meyer, Project Manager Smart Energy Concepts at the Chilean-German Chamber of Commerce and Industry (AHK Chile) says that there are various incentives for the installation of solar panels for self-consumption. These operate more at the regional or municipal level, and they can vary greatly. "One program, for example, in the North Rhine-Westphalia region pays a subsidy of 100 euros per Kilowatt/peak (kWp). In addition, there are credits with low interest rates for the implementation of renewable energies, such as from the state-owned bank KFW with an interest rate of 2.11% effective annual interest rate," he says.

    He explains that the payback time for a solar plant on the roof of a house for subsidy purposes is estimated at 20 years, however, the reality is that it is recovered in nine to 11 years. Although the period is long, "people still make the investment because they anticipate that the price of electricity will not go down - it costs over 30 euro cents per kw/hour - and because they want to become independent with clean energies", he says.

    When comparing the German context with the Chilean one, the expert affirms that "in Chile it has always been thought that subsidies are not necessary due to the natural conditions of the country" and points out that the return on average is seven to eight years, lower than in Germany.

    He says that in Chile there is a lack of information to install a solar panel project and although in his opinion it is not "so necessary" to have subsidies, "it would be important that there is easy financing, with a low interest rate, to massify it".

    Regarding regulations, Meyer comments that, in Hamburg, from 2023 "it will be mandatory to put solar panels on the roofs of buildings. This could be applicable to Chile because Hamburg has a solar radiation comparable to that of the Los Lagos region".

    He explains that the Renewable Energy Sources Act in Germany allows private individuals to inject into the grid and establishes a fixed price guaranteed the same for everyone per kWh, i.e. for those who inject all or only part of it. However, from 2023 onwards, a lower value will be paid for the injection of energy from self-consumption surpluses.

    In Chile, little exists. The country has a Net Billing law, which allows solar plants certified by the Superintendency of Electricity and Fuel to inject energy into the grid, which is then deducted from energy consumption.

    In terms of incentives, in October 2020 the Ministry of Energy launched the Casa Solar program to subsidize the installation of solar plants in homes, in a context in which there were only "five thousand houses with solar panels", says the Undersecretary of Energy, Julio Maturana.

    To date, with a budget of $ 5 billion, two calls have been made. In 2020, the program benefited 2,800 homes and the second, launched in November 2021 - ongoing - seeks to benefit 2,500 homes. They have already increased the number of systems in homes by 56% and with the second call, "we will double this figure," says Maturana.

    The installed photovoltaic capacity of both programs "is expected to be 9 MW, an annual electricity generation of 14 MWh and an estimated annual emissions reduction of 5,000 tons of Co2 equivalent (tCO2eq)," says the undersecretary.

    He points out that one of the government's proposals is to "decentralize and democratize" energy, therefore, it seeks to reach 500 MW installed of distributed generation in unitary and community systems. "Here Casa Solar is fundamental. We hope to reach 20,000 homes through the program, to which we will add financing for the incorporation of photovoltaic systems in 400 schools and health centers so that they will have self-generation energy systems during the government's term," he says.

    Self-generation in homes

    The solar panel market for homes is still limited and most of the companies cover homes and businesses. One of them is Proyecta Energía, founded in 2017 by Cedric Miralles, an electronics engineer at the Universidad Técnica Federico Santa María, and which, to date, has materialized 200 projects in homes.

    Miralles points out that the standard of these installations ranges from 15 m2 to 20 m2, and between six and 10 solar panels which generate between 400 kilowatts/month to 700 kw/month. In general, it covers between 50% and 80% of the total consumption and equal savings in the electricity bill, "but it depends on the consumption of each house and the time of the year, we receive houses with electricity bills from $ 40 thousand to $ 200 thousand", he says.

    Regarding the cost, it varies between $ 3 million and $ 5 million, and includes inputs -such as panels and power inverter- assembly and SEC certification to inject the surplus into the network, in addition to a smartphone application that allows managing information and monitoring consumption.

    And in relation to emissions reduction, a project of between 6 and 10 panels (500W each), can avoid the generation of 1.5 tons of CO2/year and 3 tons of CO2, respectively per year. Projects installed in houses range from four panels (the smallest) (2,000W) to 20 panels (10,000W).

    Miralles points out that a positive impact is that it allows decentralized generation. "I am not consuming energy that is generated in Alto Biobío where they had to intervene in national parks, but I am generating the energy myself, in my house. In the long run, this could make it less necessary to implement more hydroelectric plants.

    One concrete example is the solar project that journalist Pablo Tapia installed in his house. He says that during the pandemic he went to live on the outskirts of Santiago in an area where the electricity is constantly cut, but where there is a lot of sun. He tried to solve the problem with a benzine generator, but "it was like living with a motorcycle running in the house, with noise and smoke", he says.

    So he began to wonder how to take advantage of the sun and, after some research, he came across Proyecta Energía. Last March 23, he started operating a solar plant on the roof of his house with 14 410W panels and two 48V 3.5 kWh capacity lithium batteries to store the energy captured during the day, each with an autonomy of seven hours.

    Tapia says that the system allows him to supply almost the entire consumption of the house in 24 hours, achieving "autonomy and savings in the electricity bill". In the first bill - which does not take into account the operation of a full month of panels - the cost dropped from $80,000 to $36,000 and "it will go down more", he says.

    Another important impact, he says, is that he is generating fewer greenhouse gas emissions into the environment and "I feel I am setting a tremendous example to my children".

    On return on investment, he says this is not an issue, "if a person builds a swimming pool they don't ask themselves this question and they recover the investment when they bathe the first time. This is the same thing. I recovered the expense the day the power went out in the neighborhood and I didn't realize it," he says.

    Sodimac has solar roofs at 48 of its facilities.

    How does a solar plant work?

    The solar panels capture solar radiation and transform it into continuous energy which is fed to an inverter, and transforms it into alternating energy, which is what comes out of the sockets, explains Cedric Miralles of Proyecta Energía.

    The inverter - which is connected to the cable that arrives at the house's panel or directly to the meter - is a computer that derives the transformed energy to the house or injects it into the electrical grid automatically.

    To inject surpluses into the grid, the plant must be certified by the SEC. In this case, the electric company must change the meter to one that captures consumption and injection and "at the end of the month it makes a settlement and pays the injected surplus," says the expert.

    A solar house in Germany

    The Jüngling family has had a solar roof since 2017 on their house, located in the southern German town of Geislingen. Gerhard Jüngling, father of the family, comments that their main motivation was "to generate electricity without being dependent on anyone, and to contribute to CO2 reduction to help the environment, where we can reduce more than 7.4 tons of CO2 per year."

    To date, his investment has not been repaid, since "for this to happen, it takes 10 to 12 years," he says. The installation was done through an external company, since in Germany "it is forbidden to do it yourself".

    The house has 44 modules, each of which produces 290 watts, totaling 12.7 kWp. In their case, they received no public subsidies, since the electricity they generate is for their own use. However, Jüngling points out that "there are people who do not use the electricity they produce for themselves, but feed the grid with the electricity they produce with this photovoltaic system, and they do receive money from the government, where each kilowatt/hour is equivalent to 7 euro cents. We use the energy that we have left over for the grid.

    The energy obtained from the panels does not fully support the house, since during the night the electricity is obtained from the grid, in addition to using batteries to store the electricity, solar thermal energy and a thermal pump.

    As of July 1, Jüngling points out that in Germany it will be mandatory to install a photovoltaic system in new houses that are built.

    Solutions journalism

    • In this issue, DF includes a new article in the "Solutions Journalism" series.
    • This concept reflects a trend that seeks to bring to the forefront actions that are producing results in solving different social and economic problems.


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