Watching the clouds go by

Smart grids are pivotal to optimized energy flows in tomorrow's cities. They also involve micro-scale production — which doesn't mean that profitability or productivity requirements do not apply. So weather forecasting, practiced on an equally small time- and geographic scale, is critical. A new field for Total, which is acquiring additional skills and capabilities that promote reliable, affordable and smart energy through its participation in the IssyGrid project in France.

The city of the future, where 66 percent1 of the world's 9.7 billion2 people will live in 2050, will be denser and more populous. It will also have to meet a series of major challenges, including energy supply, waste and utilities management, and transportation efficiency, to mention just a few.

When it comes to energy, carbon responsibility needs to be added to supply, without waiting. To earn their sustainability stripes, cities of the future will have to employ an energy mix comprised mainly of non-polluting, local renewable sources, while striving to conserve energy.

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Smart grids, the future of energy

So "future energy" will be smart. More precisely, the power grids that carry it will get smart. Going digital will enable them to balance power flows between suppliers and end consumers.

And they will come with many advantages. Smart grids do a better job balancing use and production, make grids safer and facilitate the integration of renewable resources (solar, wind, biomass) into the grid. Lastly, they're a factor in cheaper energy, because managing systems as efficiently as possible optimizes consumption and production costs.

As the world transitions to new energies, the growth outlook for smart grids is significant. At the end of 2014, the U.S. market research and consulting firm Navigant Research, which provides in-depth analysis of global clean technology markets, predicted that global revenue from smart grid technologies would jump from $44.1 billion in 2014 to $70.2 billion in 20233. The figure takes into account high investment costs, because smart grid projects involve such a diverse range of stakeholders.

No one company has the capability to integrate all the know-how required alone. Partners have to develop convergent communication systems that speak the same language. This is probably the biggest technological challenge facing smart grids.

IssyGrid, a smart city laboratory

It's a challenge the IssyGrid project in Issy-les-Moulineaux, a Paris suburb, has been meeting since April 2012. A "real-world" lab and the first project of its kind in France, it has all the components of an urban smart grid. It is also an ecosystem made up of several industrial operators with municipal, building, digital or energy expertise, who are partnering with highly specialized and innovative start-ups.

Since launching in 2012, IssyGrid has powered 1,000 housing units, four office buildings, the EFB law school (École de Formation du Barreau de Paris) and part of the town's street lighting. Some of the power is generated by more than 500 square meters of photovoltaic panels, located on three sites. The electricity is used to operate the sites or fed into the public power grid. Meanwhile, data are forwarded to a smart distribution center that can determine requirements and avoid consumption peaks without ever inconveniencing users, whether residents or businesses.

When a lone cloud can cause production to slide

Because there's no question that the core focus of smart grids is end users, they have to be able to decide how much to use based on the information they receive. Are they in a period of low-carbon power production or not? Are their batteries charged or depleted? How much will the photovoltaic panels produce today, or even the next hour?

"We have to be able to say precisely, on a scale of one to 24 hours, what's going to happen in terms of solar irradiance in the next five to 60 minutes. This lets people make energy choices, notably about how much to use," explains Valérick Cassagne, photovoltaic rooftop & BIPV manager at Total. The company can supply such ultra-precise information because of its dual role as the consortium's photovoltaic solutions supplier and power production forecaster. Consumer choices can be automated or manual, such as adjusting the temperature of air conditioning or the settings of power-guzzling equipment. For example, the Sequana office tower4 turned off its air conditioning at 4 p.m. for a few hours one very hot day when the grid was stressed and the power generated was high-carbon because of a spike in usage. The temperature in the offices only crept up by 0.2 degrees Celsius. This was imperceptible to end users, while offering much bigger environmental and financial benefits. In this case, quality forecasting allowed the building manager to cool the infrastructure during "green power"(low carbon intensity) hours, to strike the best balance with "black" (high carbon intensity) hours.

Although one hour is a very short period of time, it's nonetheless a serious challenge. And there are more complications. Forecasting must be done where the sun's rays are being captured. Meaning on the roof of the building on which the photovoltaic panels are installed. Valérick Cassagne confirms that: "It's difficult, because we're talking about a timescale of around one minute. In photovoltaics, a cloud passing overhead lowers the panels' energy production by 30 to 50 percent — immediately." Batteries are installed to buffer such inevitable production fluctuations. But they're a significant expense and have to be sized accurately. "We have to find the right balance between spending on batteries and quality forecasting. The more accurate the forecasting, the smaller — and cheaper — the battery," says Valérick Cassagne. "In a way, we watch the clouds go by," he adds with a smile.

Ever more precise

Today weather data are culled from traditional — and sometimes free — websites such as Météo France. "But they aren't precise enough in terms of time windows," notes the project manager. "We're turning to specialized service providers such as Reuniwatt, a Reunion-based start-up whose data is much more detailed." But precision comes at a cost: Around 4,000 euros ($4,472) a year for a site that generates roughly 5,000 euros in photovoltaic production revenue over the same period. Not happening! "We're looking for solutions priced at around 100 euros a year, which are far more compatible with a market in which a 50 kW site requires an investment of 100,000 euros that pays for itself in 25 years and creates about 4,000 euros a year in value." Detailed weather forecasters should probably scale their services to districts or cities, rather than buildings, and create business models with that in mind. The ball is in their court. Especially, says Valérick Cassagne, as: "We have installed instruments that can validate forecasts on EFB's rooftops. They send us back data on what actually happened, enabling us to correlate predictions and actual events and gauge the quality of forecasts."

Compared to "conventional" power plants, the production sites supplying smart grids may seem tiny. But unit by unit, rooftop by rooftop, the city is undergoing a metamorphosis. "There is no technological revolution per se," notes Valérick Cassagne. "We have to bundle a wide range of different technologies and make them compatible with one another. Cities change slowly. If you figure that 1 percent of the housing stock is replaced or renovated each year, it will take another 25 or 30 years to see significant changes."

In the meantime, Total's Renewable Energies Division continues to scope out the situation. It wants to better understand the challenges of its partners, for whom data integration was "a key issue we couldn't afford to underestimate. We had to give a shared protocol and language to an assortment of information systems. Each partner provided its expertise and together, we succeeded," comments Valérick Cassagne. His parting comment: "Let's not forget that the visible part of smart grids, the user part, has to be simple and accessible, while the submerged part, the technology, functions independently."

1 Source: United Nations, July 2014.

2 Source: United Nations, 2015.

3 Smart Grid Networking and Communications.

4 Headquarters of hotel operator AccorHotels since the summer of 2016. A hundred meters tall, it can hold 2,720 people.

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