To date, the topic of storage has played a rather minor role in the energy transition in Germany. From when on, will this have to and will it change?
It made sense for us to focus on expanding renewable energies first. Unlike with renewables, however, we should not build as much storage as possible, but rather what is currently required. Every storage facility incurs additional costs, and its use causes efficiency losses. In various studies, we have been able to show quite well that, in fact, up to a share of about 50 percent renewable energies, there is no real need for storage at all from the point of view of the power grid. And long-term storage is only needed beyond a share of 80 percent renewables.
Now, however, we are exactly at the point where storage facilities are necessary in order to get away from fossil power plants. Now, there are increasingly periods when conventional power plants are not in fact needed. However, in order to actually be able to shut them down during these phases, we need storage facilities for the instantaneous, primary and secondary reserve. This is necessary to balance out fluctuations and ensure grid stability.
Another important point for me is that we always talk about storage. Viewed from the perspective of the power grid, however, we don't necessarily need storage facilities, but flexibility. In other words, if there is a lot of renewable energy, we need something to utilize the surplus power for a useful purpose. Furthermore, if there is too little electricity, we have to release power. This can also mean switching off loads. From a technical point of view, a storage facility is the ideal element for this, however, the task of balancing supply and demand can also be achieved in other ways.
In the political discussion, people also like to refer to future innovations that are necessary. Do the storage technologies for the energy transition still have to be invented?
No, the technologies are already available to us today. We have solutions for short-term storage with lithium-ion batteries and also with classic lead batteries. Long-term storage in the electrical sector is gas, i.e. hydrogen or methane produced from green electricity. Between these technologies we don't need that much more. When it comes to innovations, the question can only be: can we make the technologies more affordable in terms of lifecycle costs? Storage systems are still expensive, of course. Battery storage systems have significant investment costs that have to be amortized over their life cycle. Research must focus on finding alternatives for limited raw materials on the one hand, and on making the technologies more cost-effective in terms of lifecycle costs on the other. Investment costs, efficiency and service life, but also recycling, play an important role here.
Then let´s get specific: which storage technologies will be used for future supply security as well as grid stability?
Anything that needs to be balanced on a 24-hour basis is the domain of battery technology. Charging and discharging takes place every day, and that is where efficiency plays a major role. Therefore, you would not choose gas for a daily cycle, as the conversion from electricity to gas and back to electricity has an efficiency of only about 40 percent in the case of hydrogen as a gas. That means for every kilowatt-hour that will be returned, there will be a loss of one and a half kilowatt-hours. In comparison, a lithium-ion battery including converter achieves an efficiency of 85 to 90 percent, which is quite a different story.
On the other hand, we need a buffer for the so-called dark and wind scarce periods of up to three weeks. The energy system must, therefore, be able to supply itself from storage facilities for up to three weeks when fossil fuels are no longer available. From what we can see today, this task can only be performed by gas. In this case, the relatively low efficiency no longer plays such a decisive role. Instead, it is almost exclusively the investment costs that matter.
This can be calculated quite easily: if we use a very inexpensive stationary battery storage system, the installation costs amount to around 100 euros per kilowatt hour. If we assume a 20-year service life and need the storage unit on average once a year, then each kilowatt hour sold would have to earn an average of five euros. This does not yet include loss compensation, maintenance, repair or capital costs. The long-term average price of electricity on the stock exchange is five cents, just one percent of that. If we compare that with a gas storage facility in a salt cavern in Germany, we are worlds apart. Only around 50 cents need to be invested for one kilowatt hour of storage capacity in the cavern. Calculated over the same 20 years, each with one cycle, this results in 2.5 cents per kilowatt hour. In addition, there is the depreciation for the electrolyzer and gas turbine, but these are rather subordinate. That is perfectly okay for a long-term storage facility, which is a form of insurance cover. In this sample calculation you could also add five to ten cents per kilowatt hour for the losses that result from the poor efficiency of a hydrogen storage system, without that being a problem. Of course maintenance, repair or capital costs must also be taken into account here.
For this reason it so important to make a clear distinction between the forms of storage: short-term storage must have high efficiency above all else, and long-term storage must have low investment costs as it is so rarely used.
In your view, are there any storage technologies that are currently under the radar but have greater potential?
I would say it is more the other way around. There are still many technologies that play a role in public opinion. However, it is quite clear that these technologies will never attain economic viability.
Unfortunately, it is very brutal: For storage in the stationary sector, it is virtually only about lifecycle costs. In the mobility sector, weight still plays a major role, as does performance in terms of super-fast charging. In contrast, the requirements we have for stationary storage are all harmless. The performances are manageable, which means we need maybe half an hour, maximum four hours of electricity from the storage. From a storage perspective, the maximum currents are small. Weight and volume play a very minor role. Therefore, in the storage sector, the qualification for stationary applications is almost exclusively based on the cost factor.
Redox flow batteries are discussed from time to time as possible alternatives. However, the problem is that lithium-ion batteries have a 30-year head start on the market. In 1991, the price was perhaps $3,000 per kilowatt hour; today, the price paid by vehicle manufacturers is perhaps $100 per kilowatt hour. In other words, a factor of 30 has been gained here, largely through economies of scale in production. It is virtually impossible to catch up.
There are always discussions about technologies such as flywheels, double-layer capacitors or superconducting coils for even shorter hold-up times. However, we find that they are not economically competitive – and that is always the essential factor. In other words, technically the systems all work, but over operating times of 15 minutes or longer, these systems are simply not economical. For this reason we really only see them in special applications and less for the system integration of renewables. An example would be a container crane that lifts a container every minute and puts it down again and has a high peak power demand for this or a regenerative power demand through recuperation. A similar application exists, for example, in the substations of subways or tramways. In all cases, peak load capping is the motivation and not the integration of renewable energies.
In your view, will electric cars also play a noticeable role in balancing out fluctuations in demand within a day?
If I just take the smallest wallbox with three kilowatts as the charging station and assume 40 million cars, I get 120 gigawatts of power. If you compare that with the six gigawatts we have in pumped storage power plants or the 80 gigawatts of peak power, you can immediately see where the potential is. And it's absolutely clear: vehicle batteries don't get broken from driving, but from standing around. If we don't succeed in utilizing this huge amount of investment in the field of electric cars, it would be extremely counterproductive. It would mean that we would have to build additional storage facilities, which would cost additional money and make electricity and energy more expensive for all of us.
I not only see this as a great opportunity, but even as a necessity. On average, a vehicle runs for one and a half hours a day. Therefore, there are huge capacities available most of the time.
Hadi sasa, mada ya kuhifadhi imekuwa na jukumu dogo katika mabadiliko ya nishati nchini Ujerumani. Kuanzia lini, hii itabidi na itabadilika? Ilikuwa na maana kwetu kuzingatia kupanua nishati mbadala kwanza. Tofauti na nishati mbadala, hata hivyo, hatupaswi kujenga kuhifadhi nyingi iwezekanavyo, lakini badala yake kile kinachohitajika sasa. Kila kituo cha kuhifadhi hutokeza gharama za ziada, na matumizi yake husababisha hasara ya ufanisi. Katika masomo mbalimbali, tumeweza kuonyesha vizuri kwamba, kwa kweli, hadi sehemu ya nishati mbadala ya karibu 50%, hakuna haja halisi ya kuhifadhi kabisa kutoka kwa mtazamo wa mtandao wa umeme. Kuhifadhi kwa muda mrefu kunahitajika zaidi ya 80% ya nishati mbadala. Hata hivyo, sasa, sisi ni hasa katika hatua ambapo vifaa vya kuhifadhi ni muhimu ili kupata mbali na mitambo ya nishati ya mafuta. Sasa, kuna vipindi vingi zaidi ambapo mitambo ya umeme ya kawaida haihitajiki. Hata hivyo, ili kuweza kuzima wakati wa hatua hizi, tunahitaji vifaa vya kuhifadhi kwa ajili ya akiba ya papo hapo, ya msingi na ya sekondari. Hii ni muhimu ili kusawazisha fluctuations na kuhakikisha utulivu wa gridi. Jambo jingine muhimu kwangu ni kwamba sisi daima majadiliano kuhusu kuhifadhi. Kuangalia kutoka kwa mtazamo wa gridi ya umeme, hata hivyo, hatuna lazima ya vifaa vya kuhifadhi, lakini kubadilika. Kwa maneno mengine, ikiwa kuna nishati nyingi inayobadilika, tunahitaji kitu cha kutumia nishati ya ziada kwa kusudi muhimu. Kwa kuongezea, ikiwa kuna umeme mdogo sana, ni lazima tutolee nguvu. Hii pia inaweza kumaanisha kuzima mizigo. Kutoka kwa mtazamo wa kiufundi, kituo cha kuhifadhi ni kipengele bora kwa ajili ya hii, hata hivyo, kazi ya kusawazisha ugavi na mahitaji pia inaweza kupatikana kwa njia nyingine. Katika majadiliano ya kisiasa, watu pia wanapenda kurejelea uvumbuzi wa baadaye ambao ni muhimu. Je, teknolojia za kuhifadhi kwa ajili ya mabadiliko ya nishati bado zinahitaji kuvumbuliwa? Hapana, teknolojia hizo zinapatikana tayari leo. Tuna ufumbuzi kwa ajili ya kuhifadhi muda mfupi na betri lithiamu-ion na pia na betri classic risasi. Uhifadhi wa muda mrefu katika sekta ya umeme ni gesi, yaani Hifadhi ya metani ya hidrojeni na metani ya gesi ya kijani Pamoja na teknolojia hizi hatuna haja ya mengi zaidi. Kwa habari ya uvumbuzi, swali linaweza kuwa tu: tunaweza kufanya teknolojia kuwa nafuu zaidi kwa suala la gharama za mzunguko wa maisha? Mifumo ya kuhifadhi bado ni ghali, bila shaka. Mifumo ya kuhifadhi betri ina gharama kubwa za uwekezaji ambazo zinapaswa kuondolewa katika mzunguko wao wa maisha. Utafiti lazima kuzingatia kutafuta mbadala kwa ajili ya malighafi mdogo kwa upande mmoja, na kufanya teknolojia zaidi gharama ya ufanisi katika suala la gharama za mzunguko wa maisha kwa upande mwingine. Gharama za uwekezaji, ufanisi na maisha ya huduma, lakini pia kuchakata, kucheza jukumu muhimu hapa. Kisha hebu kupata maalum: ambayo teknolojia ya kuhifadhi itatumiwa kwa ajili ya usalama wa usambazaji wa baadaye kama vile utulivu wa gridi? Kwa hivyo, kila kitu kinachohitaji kusawazishwa kwa masaa 24 ni uwanja wa teknolojia ya betri. Kuchaji na kutolewa hutokea kila siku, na hapo ndipo ufanisi unafanya jukumu kubwa. Kwa hiyo, haipaswi kuchagua gesi kwa mzunguko wa kila siku, kama kubadilisha kutoka umeme kwa gesi na nyuma kwa umeme ina ufanisi wa asilimia 40 tu katika kesi ya hidrojeni kama gesi. Kwa kila kilowatt-saa ambayo inapatikana, kuna hasara ya kilowatt-saa moja na nusu. Kwa kulinganisha, betri ya lithiamu-ion, ikiwa ni pamoja na converter, inapata ufanisi wa asilimia 85 hadi 90, ambayo ni hadithi tofauti kabisa. Kwa upande mwingine, tunahitaji buffer kwa kipindi kinachoitwa giza na upepo mdogo wa hadi wiki tatu. Kwa hiyo, mfumo wa nishati lazima uweze kujitegemea kutoka kwa vifaa vya kuhifadhi kwa hadi wiki tatu wakati mafuta ya mafuta hayapatikani tena. Kwa kile tunachoweza kuona leo, kazi hii inaweza tu kufanywa na gesi. Katika kesi hii, ufanisi wa chini kwa kulinganisha haufanyi kazi muhimu tena. Badala yake, ni karibu peke ya gharama za uwekezaji kwamba jambo. Hii inaweza kuhesabiwa kwa urahisi: ikiwa tunatumia mfumo wa kuhifadhi betri ya chini sana, gharama za ufungaji ni karibu € 100 kwa kila kilowatt saa. Ikiwa unadhani maisha ya huduma ya miaka 20 na unahitaji kifurushi cha kuhifadhi kwa wastani mara moja kwa mwaka, basi kila kilowatt saa inayouzwa inapaswa kupata wastani wa euro tano. Hii bado haijumuishi fidia ya hasara, matengenezo, ukarabati au gharama za mtaji. Kwa mfano, bei ya umeme kwa muda mrefu katika soko la hisa ni senti tano, asilimia moja tu ya hiyo. Kwa mfano, ikiwa tunachunguza jinsi ya kuhifadhi gesi katika pango la chumvi huko Ujerumani, tunaona kwamba ni rahisi sana. Kwa mfano, inahitaji tu dola 50 kwa kila kilowatt-saa ya kuhifadhi katika pango. Kwa mfano, kwa miaka 20 ya mzunguko mmoja, kila mzunguko una thamani ya senti 2.5 kwa kila kilowatt saa. Kwa kuongezea, kuna depreciation kwa ajili ya electrolyzer na turbine gesi, lakini hizi ni badala ya chini. Hii ni sawa kabisa kwa ajili ya kituo cha kuhifadhi muda mrefu, ambayo ni aina ya bima ya bima. Katika mfano huu wa hesabu unaweza pia kuongeza senti tano hadi kumi kwa kila kilowatt saa kwa hasara inayotokana na ufanisi duni wa mfumo wa kuhifadhi hidrojeni, bila kuwa na tatizo. Bila shaka matengenezo, ukarabati au gharama za mtaji lazima pia kuzingatiwa hapa. Kwa sababu hii ni muhimu sana kutofautisha kati ya aina ya kuhifadhi: kuhifadhi kwa muda mfupi lazima kuwa na ufanisi wa juu juu ya kila kitu kingine, na kuhifadhi kwa muda mrefu lazima kuwa na gharama za uwekezaji za chini kwa sababu hutumiwa mara chache sana. Kwa maoni yako, kuna teknolojia yoyote ya kuhifadhi ambayo kwa sasa iko chini ya rada lakini ina uwezo mkubwa? Ningesema ni kinyume chake. Bado kuna teknolojia nyingi ambazo zina jukumu katika maoni ya umma. Hata hivyo, ni wazi kabisa kwamba teknolojia hizi kamwe kufikia ufanisi wa kiuchumi. Kwa bahati mbaya, ni kikatili sana: Kwa ajili ya kuhifadhi katika sekta ya stationary, ni karibu tu kuhusu gharama za mzunguko wa maisha. Katika sekta ya uhamaji, uzito bado ina jukumu kubwa, kama vile utendaji katika suala la malipo super-haraka. Kinyume chake, matakwa tunayo kwa ajili ya kuhifadhi mahali pa kukaa si yenye madhara. "Kama matokeo ya utafiti yanaonekana kuwa ya kutosha, tunaweza kusema kwamba tunahitaji nusu saa ya umeme kutoka kwa hifadhi ya umeme.""" Kutoka mtazamo wa kuhifadhi, mikondo ya juu ni ndogo. Uzito na kiasi hutimiza fungu dogo sana. Kwa hiyo, katika sekta ya kuhifadhi, sifa kwa ajili ya maombi ya kudumu ni karibu peke kulingana na sababu ya gharama. Redox mtiririko betri ni kujadiliwa mara kwa mara kama mbadala iwezekanavyo. Hata hivyo, kwa mujibu wa utafiti huo, betri za lithiamu-ion zinaweza kuuzwa kwa muda wa miaka 30 kabla ya kutolewa. Mwaka 1991 bei ilikuwa karibu dola za Marekani za kila kilowatt saa, lakini leo bei ya magari ni karibu dola za Marekani za kila kilowatt saa. Kwa maneno mengine, sababu ya 30 imepatikana hapa, kwa kiasi kikubwa kupitia uchumi wa kiwango katika uzalishaji. Ni vigumu sana kukabiliana na hali hiyo. Kuna daima majadiliano kuhusu teknolojia kama vile flywheels, capacitors double-safu au coils superconducting kwa muda mfupi zaidi kushikilia-up. Hata hivyo, tunapata kwamba wao si ushindani kiuchumi <unk> na kwamba ni daima sababu muhimu. Kwa maneno mengine, kiufundi mifumo yote inafanya kazi, lakini kwa muda wa uendeshaji wa dakika 15 au zaidi, mifumo hii sio ya kiuchumi. Kwa sababu hii sisi kweli tu kuona yao katika maombi maalum na chini kwa ajili ya mfumo wa ushirikiano wa nishati mbadala. Mfano wa crane inaweza kuwa crane ya kontena ambayo huinua kontena kila dakika na kuiweka tena na ina mahitaji ya juu ya nguvu kwa ajili ya hii au mahitaji ya nguvu ya kuzaliana kupitia kupona. Matumizi kama hayo yapo, kwa mfano, katika vituo vya chini ya ardhi au tramu. Katika visa vyote, kilele cha mzigo ni kichocheo na si ushirikiano wa nishati mbadala. Je, unafikiri magari ya umeme yatakuwa na jukumu muhimu katika kusawazisha mabadiliko ya mahitaji ya siku moja? Ikiwa tu tutachukua sanduku dogo la ukuta lenye kilowati 3 kama kituo cha kuchaji na kudhani magari milioni 40, nitapata nguvu ya gigawati 120. "Kama ukilinganisha na nguvu za umeme za gigawati 6 za pampu za kuhifadhi, au nguvu za kilele za gigawati 80 za pampu, unaweza kuona mara moja ni wapi uwezekano wa umeme.""" Na ni wazi kabisa: betri za magari hazivunjwi kwa kuendesha gari, lakini kwa kusimama karibu. """Ikiwa hatuwezi kufanikiwa katika kutumia kiasi hiki kikubwa cha uwekezaji katika uwanja wa magari ya umeme, itakuwa na athari mbaya sana." "Hiyo inamaanisha kwamba tunapaswa kujenga vifaa vya ziada vya kuhifadhi, ambayo itagharimu pesa za ziada na kufanya umeme na nishati kuwa ghali zaidi kwa sisi sote. """ Mimi si tu kuona hii kama fursa kubwa, lakini hata kama uhitaji. Kwa wastani, gari hutumia saa moja na nusu kwa siku. Kwa hiyo, kuna uwezo mkubwa inapatikana zaidi ya muda.