Weight of seasonal demand in 100% electric scenario – pv magazine International

According to pv magazine USA.

Most building decarbonization models do not take into account seasonal variations in energy demand for heating or cooling. Therefore, it is difficult to predict what consequences 100% electric heating will have on the grid, particularly during peak consumption.

A recent study by researchers from the Boston University School of Public Health (BUSPH), the Harvard Chan School of Public Health, Oregon State University, and the Home Energy Efficiency Team (HEET), a nonprofit organization, examined seasonal changes in energy demand . She noticed that monthly energy consumption fluctuates significantly and reaches a maximum in the winter months.

The study, titled “Inefficient Building Electrification Will Require Massive Construction of Renewables and Seasonal Energy Storage,” published in Scientific reports, presented a new model consisting of several building electrification scenarios. She concluded that current renewable energy sources will struggle to meet peak winter energy demand if buildings switch to low-efficiency electric heating. Its results highlight the need to install more efficient heating technologies, such as geothermal heat pumps.

“Our work highlights the degree to which energy demand in buildings fluctuates, as well as the benefits of using very high-efficiency heating technologies when electrifying buildings,” explained Jonathan Buonocore, associate professor of environmental health at BUSPH and lead author of the study.

“Historically, these fluctuations in energy demand have been largely accommodated by gas, fuel oil and wood, which can be stored year-round and used in the winter. Homes that are electrified and the electrical system that feeds them must be able to provide the same service, namely reliable heating throughout the winter. More efficient electrical technologies will reduce the electrical load on the grid and increase the ability to meet this heating demand from renewable sources that do not use combustion. »

Analyzing building energy use from March 2010 to February 2020, the study found that average monthly energy use in the United States, based on current fossil fuel use and future winter electricity use, varies by a ratio of 1 to 1.6. , demand was at its lowest in May and peaked in January.

The researchers modeled these seasonal fluctuations on a curve called the “Falcon Curve,” which illustrates fluctuations in monthly energy consumption and is shaped like a falcon. According to the data, winter heating demand increases energy demand to the highest levels in December and January with a secondary peak in July and August for cooling and the lowest levels in April, May, September and October.

Current total monthly electricity demand by sector from March 2010 to February 2020 and projections of changes in total building energy demand under different electrification scenarios based on different COP technologies.

Image: Boston University School of Public Health, Scientific Reports, Creative Commons CC BY 4.0

The researchers then calculated how much additional renewable energy, including solar and wind power, would need to be produced to meet this increased demand for electricity. To cover winter peaks without storage, load shedding or other grid load management strategies, they said, would need to multiply wind generation by 28 or solar generation by 303 per month. January.. They then added more efficient renewables, including aerothermal or geothermal heat pumps, and calculated that it would then be enough to multiply wind generation by 4.5 and winter solar generation by 36, which would reduce the additional energy demand on the grid, and , therefore, “flattens” the curve of the hawk.

“This work clearly demonstrates the role of technology in decarbonization, both on the demand side and on the supply side,” said Pariher Salimifard, a study co-author and associate professor at Oregon State University’s College of Engineering.

Among the examples of energy supply technologies, she cites geothermal heating, as well as technologies that can provide 24/7 energy, including renewable energy sources combined with long-term storage, decentralized energy sources of any size, and electricity generation using geothermal energy when possible.

“This can be combined with demand-side (i.e. building-level) technologies such as passive and active energy efficiency measures, peak load reduction and energy storage in buildings. Activities at the building level can reduce their overall energy consumption by reducing both base and peak demand, as well as smoothing fluctuations in consumption and therefore smoothing the hawk curve, explains Paricher Salimifard.

Zeineb Magawi, co-author of the study and co-director of HEET, a non-profit incubator for climate solutions, continues: “The hawk curve draws our attention to the key relationship between the choice of electrification technology for a building and the impact of that electrification. in our electrical network. »

Zeyneb Magawi points out that this research does not yet quantify this relationship based on measured seasonal performance curves for certain specific technologies or for time scales or regions with greater granularity. Nor do they appreciate the many strategies and technologies that can help tackle decarbonisation, all of which need to be taken into account when planning it.

However, according to Zeineb Magawi, this study indicates that “the use of a strategic combination of heat pump technologies (aerothermal, geothermal and grid-connected) and long-term storage will help electrify buildings more efficiently, economically and equitably. . The hawk curve shows us a faster path to a cleaner and healthier energy future. »

“Our study highlights the fact that, given the seasonal variations in energy consumption as they appear on the falcon curve, measures taken to electrify our buildings must be accompanied by a commitment to use efficient technologies to ensure that efforts by decarbonizing buildings to maximize climate and health benefits,” says Joseph G. Allen, lead study author and associate professor of exhibition evaluation and director of the Healthy Buildings Program at

One of the most dramatic changes, even with highly efficient electrification, is the likely shift from summer peaks to winter peaks in the US power system. According to the researchers, for the electrification of buildings to constitute “a healthy decarbonization of the energy used by buildings, additional electricity demand must be met by non-combustible renewable energy sources, which, according to our most optimistic projections, will require a 4.5-fold increase in solar energy”.

Currently, seasonal fluctuations are mainly covered by the fossil fuel system with long-term storage. In an all-electric scenario, long-term electricity storage can play an important role in helping renewables meet the demand of newly electrified buildings.

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