Saving for the future

Renew­able ener­gies are volatile. Decar­boniza­tion will not be possible without storage tech­nolo­gies across all grid levels.

Environ­mental protec­tion and the reduc­tion of green­house gases, partic­u­larly CO 2 , require far-reaching changes in energy produc­tion around the globe. The expan­sion of renew­able ener­gies, espe­cially solar and wind energy, play a key role in the energy revo­lu­tion, because the supply of these environ­mentally friendly energy sources vastly exceeds the current global need for primary energy, currently at about 170,000 terawatt hours (see ONLOAD 07).

According to data acquired by the IEA (Inter­na­tional Energy Agency), emis­sions-free power already accounts for approx­i­mately 37% of the power flowing through grids around the world. However, elec­tric energy only makes up a fifth of the total global energy consump­tion. There­fore, how renew­able sources can substi­tute conven­tional ones in the trans­port and heating sectors is also crucial for the energy revo­lu­tion.

There­fore, how renew­able sources can substi­tute conven­tional ones in the trans­port and heating sectors is also crucial for the energy revo­lu­tion.

In order to reach our climate goals, a whole array of chal­lenges must be over­come. In the words of Markus Riepl, who develops solu­tions for the grids of the future at Rein­hausen: “Many ques­tions are about how the grids of the future can trans­port this massive amount of energy, and how the volatile produc­tion of solar and wind power can be aligned with current needs in the right place at the right time. These ques­tions have both global and regional dimen­sions.”

In the future, many indus­tri­al­ized nations, such as Germany, will have to import “green energy” in the form of “green hydrogen” produced in windy and sunny regions. At the same time, grid capac­i­ties are already reaching their limits and cannot always trans­port envi­ron­men­tally friendly power from the producer to the consumer as needed. One option for offset­ting these fluc­tu­a­tions are energy accu­mu­la­tors. Below, this article shows how grid prob­lems asso­ci­ated with renew­able ener­gies can be solved with storage systems—from high-voltage and extra-high-voltage to medium-voltage and low-voltage levels.

The chal­lenge of sector coupling

Even at the extra-high-voltage level, battery storage can buffer trans­mis­sion bottle­necks in grids. For example, in Germany, elec­tricity has to get from off-shore wind parks in the windy north to high-consump­tion areas in the south. While oper­a­tors are constantly expanding trans­mis­sion grids, this alone is not enough. The trans­mis­sion power must also be opti­mized using what are called “grid boosters”. These are gigantic battery systems in the power range of several hundred megawatts.

For context: Trans­porting large amounts of elec­tricity from the north to the south over lines results in over­loading indi­vidual line sections again and again, which makes expen­sive redis­patch measures neces­sary. This means that producers upstream of a bottle­neck must reduce their produc­tion and those down­stream of the bottle­neck must increase their produc­tion by the same amount. The costs for these measures add up to more than 100 million euros annu­ally in Germany alone.

Power gener­a­tion and consump­tion: When balancing the gaps or surpluses between gener­a­tion and consump­tion, redis­patch costs arise. Grid boosters help to mini­mize these.

Grid boosters help balance out these gaps by saving the excess quan­ti­ties that occur upstream of bottle­necks and cannot be trans­ported, nd then providing the power down­stream of the bottle-necks. Since this all happens within an extremely fast response time, safety reserves in the grids intended for these kinds of malfunc­tions can be used for elec­tricity trans­port.

Grid boosters for trans­mis­sion grids

Due to the depen­dence on wind and weather, there is usually either too much or too little elec­trical energy avail­able. Grid oper­a­tors want to offset this by coupling or inter­locking the energy sectors of elec­tricity, heat and transport—using the energy source of gas. Excess renew­able energy is decou­pled to the trans­port and heating sectors using power- to-gas or power-to-heat systems.

The gas grid has enor­mous storage capacity for this. For example, the hydrogen produced with renew­able energy in fuel cells for cars or through conven­tional utiliza­tion in natural gas consumers can reduce damaging green­house gas emis­sions.

Professor Veronika Grimm of the Univer­sity of Erlangen-Nurem­berg is one of the leading forces behind sector coupling in Germany. In an inter­view with the online plat­form sech­snull. de, she explains that green hydrogen in partic­ular will play a crucial role when it comes to the decar­boniza­tion of the trans­port and heating sectors.

The prin­ciple of power-to-gas tech­nology

For this renew­able energy specialist, it is also clear that there can be no energy revo­lu­tion without inter­na­tional connect­ed­ness. “As an indus­tri­al­ized nation, we will still not be self-suffi­cient in a 100 percent renew­able world. We will import hydrogen and synthetic energy sources that were produced in preferred regions all around the world,” says Prof. Grimm.

Buffering with commu­nity batteries

Today, stationary accu­mu­la­tors, also known as commu­nity batteries, usually buffer the fluc­tu­ating amounts produced by renew­able energy sources on the medium-voltage level, thus contributing signif­i­cantly to the energy revo­lu­tion. They offer totally new oppor­tu­ni­ties for energy and load manage­ment in indus­trial oper­a­tions and distri­b­u­tion grid sections.

Wind or solar parks can be coupled to produc­tion units using these energy accu­mu­la­tors, allowing them to bring energy into the grids constantly and predictably. They help stabi­lize micro­grids or poorly devel­oped grids by compen­sating for fluc­tu­ating load and infeed amounts. From an economic point of view, commu­nity batteries make sense at many node points on the grids, says Rein­hausen expert Markus Riepl.

“Grid oper­a­tors avoid invest­ment in grid expan­sion, and suppliers of wind and solar energy can use the market imbal­ances to sell their elec­tricity when it brings in the most profit. Power stations can create reserves and compen­sate for demand peaks in the grid.”

The battery inverter combines three func­tions in a single unit: storage, reac­tive power compen­sa­tion and active filtering. Due to this system service capa­bility, these inverters are clas­si­fied as grid compo­nents by the regu­la­tory authority. This clas­si­fi­ca­tion offers advan­tages to the oper­ator in terms of invest­ment costs and storage manage­ment. Remote regions with a weak grid connec­tion can also achieve a more stable power supply using storage tech­nology.

Energy storage systems (ESS) can store energy produced by various producers, like solar and wind systems or diesel gener­a­tors, and output it to the grid as needed. As a result, these systems guar­antee a smooth, contin­uous power supply. This requires inverter solu­tions, such as GRIDCON® PCS from Rein­hausen, for example, which Autarsys installs in battery systems that are currently being used in the power supply of a remote area in the Philip­pines (read more on this in online issue 05

Andreas Plenk of the Dutch stor age system manu­fac­turer Alfen sees even more versa­tile appli­ca­tions for battery systems. “More and more Euro­pean cities are setting up green zones and want to ban diesel gener­a­tors for envi­ron­mental reasons. But markets, festi­vals and large events still need to be supplied with elec­tricity. We have a similar situ­a­tion at ports. Green zones are set up here in order to reduce the number of diesel gener­a­tors port oper­a­tors and ship­ping compa­nies need. In this way, new markets are currently emerging.”

Charging stations relieve distri­b­u­tion grids

The energy trans­for­ma­tion cannot be done without elec­tric mobility, at least as an inter­me­diate step. Analysts expect that, by 2030, there will be more elec­tric vehi­cles on the road in most indus­tri­al­ized coun­tries than those with combus­tion engines. In fact, Cali­fornia would like to get rid of conven­tional vehi­cles entirely by that point. For distri­b­u­tion grids, in partic­ular, this devel­op­ment presents tremen­dous chal­lenges which can only be mastered with intel­li­gent charging infra­struc­ture.

For example, expen­sive expan­sion of line capac­i­ties would be neces­sary in many cases in order to charge multiple vehi­cles in a parking garage or public parking spaces. The alter­na­tive is charging stations that keep a battery ready and there­fore accel­erate the charging process while simul­ta­ne­ously relieving the low-voltage grids. There is a global market here for which Rein­hausen is providing solu­tions.

This concept can also benefit from swarm intel­li­gence. The fluc­tu­ating, weather-depen­dent energy produc­tion from renew­able energy sources can also balance fluc­tu­a­tions on the local grid level through smart battery solu­tions. For this purpose, vehi­cles in their down­times provide their battery capacity to the power grid in the event of bottle­necks. In turn, in cases where the power grid would have more than enough energy to supply to the vehi­cles, supply and produc­tion peaks could be smoothed over. Battery storage can there­fore help master the chal­lenge of the energy revo­lu­tion on all grid levels—from high-voltage grids to local grids. Rein­hausen wants to do its part here.


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