< b >< span data – contrast =” auto “> Every power – savvy consumer knows : r span > b >< b >< span data – contrast =” auto “> un your electricals in the middle of the night . Specialist tariffs have trained consumers to use electricity in the hours of low demand , traditionally between midnight and dawn . But as the energy transition progresses , these low – power hours have crept away from their usual homes . How have transmission system operators fought these Sunday afternoon blues ? span > b >

< span data – contrast =” auto “> In 2020 ,  power demand fell   to   all span >< span data – contrast =” auto “>- span >< span data – contrast =” auto “> time lows . As the pandemic spread across developed nations ,  electricity transmission systems operators   saw   record – breaking low days .  On the island of Great Britain , transmission system operator   National Grid ESO   saw   consumer   power demand   fall to 13 . 4GW   on   28 June , at 5 : 30am .  This  ‘ trough ’  was a new low for consumer demand ,  2 . 4GW below   the   pre – 2020   record . span >

< span data – contrast =” auto “> If   any time could   set a new   low for consumer demand ,  the crack of dawn on a warm summer morning during a pandemic   would be the time network operators expect .  At the time ,  National Grid ESO   used   pumped hydropower storage   and exports via international interconnectors   to increase   the   network ’ s   load . span >

[ caption id =” attachment_134385 ” align =” aligncenter ” width =” 620 “]< img class =” wp – image – 134385 ” src =” https :// www . power – technology . com / wp – content / uploads / sites / 7 / 2021 / 05 / 41343452181_541e3e2991_k – 450×340 . jpg ” alt =” Pumped hydro station near Moelwyn Mawr , Wales .” width =” 620 ” height =” 349 ” /> Pumped hydro stations provide energy demand when it is needed , but cannot answer all calls . Credit : Andrew / Flickr under CC BY 2 . 0 .[/ caption ]

< span data – contrast =” auto “> This extra   demand   prevented   the   night of low customer demand   from being   the   grid ’ s   lowest point over the summer .  That came   on a bank holiday in May ,  but   unusually ,  it came at three o ’ clock in the afternoon . span >

< span data – contrast =” auto “> This time   marked one of the lowest   power   draws in the country ’ s modern history .  Over 2020 , National Grid ESO   span >noted several occasions< span data – contrast =” auto “>  where   the transmission system saw its lowest demand in the early afternoon .  We spoke to   Julian Leslie , head of networks , to ask how the company addresses the changing face of power . span >

How renewable generation changes transmission network operations

< span data – contrast =” auto “> Leslie explained : “ Over the last five or six years ,  we ’ ve seen   much more embedded   renewable   generation connecting to the distribution system  [ outside of the high – voltage transmission system ].  This comes   either as large   solar   fields or as domestic solar on people ‘ s roofs . span >

< span data – contrast =” auto “>“ The phenomena we ‘ re seeing now is that , on a Sunday afternoon , there is so much embedded generation that , from our perspective , it effectively offsets consumer demand . That makes the transmission system demand lower at around 2 or 3 o ‘ clock on a Sunday afternoon [ than overnight ]. It ‘ s a real shift , just because at five o ‘ clock on a Sunday morning , there isn ‘ t the same amount of solar generation that there is at three o ‘ clock on a Sunday afternoon . span >

< span data – contrast =” auto “>“ We saw it in 2019 , but we saw it more often in 2020 because overall demand was suppressed   by   Covid – 19 . At the minute , it span >< span data – contrast =” auto “>’ span >< span data – contrast =” auto “> s sort of 3 span >< span data – contrast =” auto “>% span >< span data – contrast =” auto “>- 4 % below what we would have forecasted   it   to   normally be . As we come into this summer , we ‘ re expecting demand to return to roughly where it would have been before Covid – 19 . span >

< span data – contrast =” auto “>“ But in the meantime , there ‘ s two years ’  more solar PV   installed   on people ’ s   roo span >< span data – contrast =” auto “> f span >< span data – contrast =” auto “> s , and a few more built in the farmer ‘ s fields . All of that works towards   counterbalancing   the   transmission   demand we see on   a   Sunday afternoon .” span >

What can transmission system operators do to avoid low power?

< span data – contrast =” auto “> Just as happened during the consumer demand trough in June , network operators   can   work with the industry to create extra demand .  In that case , pumped   hydropower reserves and pre – arranged   international exports created 3 . 8GW of extra transmission demand .  This represents   more than 10 % of average   daily demand for the country , and so dramatically alters the   power dynamics of the system . span >

[ caption id =” attachment_134381 ” align =” aligncenter ” width =” 620 “]< img class =” wp – image – 134381 ” src =” https :// www . power – technology . com / wp – content / uploads / sites / 7 / 2021 / 05 / CreditNationalGrid – Interconnector – IFA2 – PR – High – Res – min – 450×340 . jpg ” alt =” IFA2 interconnector transformers ” width =” 620 ” height =” 413 ” /> The landing site of the IFA2 interconnector , linking Britain and France . Credit : National Grid .[/ caption ]

< span data – contrast =” auto “> However , pumped hydropower cannot act as an infinite reservoir of power . If pumped hydro operators fill their reserves in the afternoon , stations cannot turn on again late at night , when energy prices could have fallen further . For this reason , operators and grid balancers have remained wary of using pumped hydro during afternoon lulls . span >

< span data – contrast =” auto “> Leslie elaborated : “ We can instruct pumps to pump , but it makes sense for them to do that anyway , because of low energy prices . We have many more storage batteries to take advantage of that , and on – the – spot tariffs are a great example of consumers getting the benefit . span >

< span data – contrast =” auto “>“ span >< span data – contrast =” auto “> Other than that , we need to make sure that we ‘ ve got the right balance of energy on the system , so that we have the tools and the flexibility that we need , if we were at a very low point , to  [ be ready to ]  lose a whole bunch of demand or our bunch of generation . span >

< span data – contrast =” auto “>“ That becomes quite challenging at low demand levels , but we ‘ ve got the tools , we ‘ ve got the processes in place , and we demonstrated through last summer that they work effectively .” span >

“How do you meet the nation’s power demands with little wind or sun?”

< span data – contrast =” auto “> Last summer , National Grid ESO implemented a   market system allowing to pay suppliers   span >< i >< span data – contrast =” auto “> not span > i >< span data – contrast =” auto “>  to generate .  This   Optional   Downward   Flexibility   Market   enabled balancers to suppress power supply just as Covid – 19 suppressed demand .  Some interested parties have said   span >< span data – contrast =” auto “> that   span >< span data – contrast =” auto “> this system   is   span >‘not sustainable’< span data – contrast =” auto “>, but   it demonstrated   the role of   communication in future balancing . span >

[ caption id =” attachment_105075 ” align =” aligncenter ” width =” 620 “]< img class =” wp – image – 105075 ” src =” https :// www . power – technology . com / wp – content / uploads / sites / 7 / 2019 / 10 / About_us_Sub_page_Green_energy_is_now_cheaper_than_black_Top_hero – 450×340 . png ” alt =”” width =” 620 ” height =” 349 ” /> The UK uses some of the world ‘ s largest offshore wind fields , such as Hornsea One , off the English coast . Source : Ø rsted .[/ caption ]

< span data – contrast =” auto “> Similar systems have become part of the ESO’s five-point plan to manage congestion on the transmission system .  span >< span data – contrast =” auto “> I span >< span data – contrast =” auto “> n the future span >< span data – contrast =” auto “>  however span >< span data – contrast =” auto “>, the balancers hope to control power demand , not just power supply . Leslie said : “ If people were able to control their demand and bring demand on , as opposed to us constraining off wind and solar , then obviously that would be part of that market . span >

< span data – contrast =” auto “>“ We see that very much as part of the future we are working on as part of this five – point plan . One point looks at a regional flexibility market , which would reward and encourage   span >< span data – contrast =” auto “> controllable demands with a better market . If you ’ ve got a large industrial process or a fleet of batteries ,  this   would be   a mechanism for   you   to get engaged with us . span >

< span data – contrast =” auto “>“ That system can work within the day , just like pumped hydro . The gap at the moment is really long – term storage , for when you get two or three weeks of no wind and little sun . How do you meet the nation ‘ s demands at that point ?” span >

Grid-scale power storage “offers alternative to transmission system investment”

< span data – contrast =” auto “> Equinor and SSE recently announced their intentions to develop a hydrogen – fired plant in the UK , which would   tie into the devolved Scottish Parliament ’ s   intentions to explore hydrogen generation . Leslie said   span >< span data – contrast =” auto “> that   span >< span data – contrast =” auto “> energy storage in Scotland could prove key , as the country ’ s large renewable generation   gives it great opportunity for grid – scale   battery farms . span >

< span data – contrast =” auto “> On a wider level , he said : “ I think there will be grid scale storage locally ;  I think the distribution network operators , with their flexibility markets , will be looking to storage as an alternative to regional or local network investment . span >< span data – ccp – props =”{& quot ; 201341983 & quot ;: 0 ,& quot ; 335559739 & quot ;: 160 ,& quot ; 335559740 & quot ;: 259 }”>  span >

< span data – contrast =” auto “>“ In the same way ,  we are looking to transmission grid – scale storage with a two – to four – week duration as an alternative , maybe , to transmission network investment . We need a whole range of different storage solutions , both locally and nationally , at the transmission level .” span >

< span data – contrast =” auto “> In the long   term , grid balancers put their faith in on – the – spot power   domestic   tariffs to change consumer prices based on supply . These would offer preferential rates to consumers using   power during transmission grid troughs . At the same time , these would increase bills for those using power at peak hours . span >

< span data – contrast =” auto “> The British energy network has started changing its network infrastructure to allow these tariffs to become more widespread and faster to act . Despite widespread use of digital energy meters , few on – the – spot domestic consumer tariffs currently exist . span >

[ caption id =” attachment_134384 ” align =” aligncenter ” width =” 620 “]< img class =” wp – image – 134384 ” src =” https :// www . power – technology . com / wp – content / uploads / sites / 7 / 2021 / 05 / 5125852229_a9e4be946b_k – 450×340 . jpg ” alt =” Smart meter ” width =” 620 ” height =” 428 ” /> ‘ Smart ‘ digital meters allow domestic consumers to track and optimise their energy use . Credit : Edinburgh Greens under CC BY 2 . 0 .[/ caption ]

< span data – contrast =” auto “> Those   currently available   advertise that ,  during   periods of high supply ,  negative pricing allows   consumers to earn money by using electricity .  This has remained relatively rare , but as the share of renewables used for generation increases , should consumers expect more negative pricing ? span >

Should UK power consumers expect more negative prices? 

< span data – contrast =” auto “> Leslie answered : “ There ‘ s more and more wind being built every week . Overall demand across the year is rising , but peak demand isn ‘ t , and therefore we will get more periods with more wind than the market needs . span >

< span data – contrast =” auto “>” Because of the subsidy regime that we have , wind farms get paid when their blades are turning , so they just want to operate . They ‘ ll put in negative pricing into the market , which will ultimately drive behaviours span >< span data – contrast =” auto “> that span >< span data – contrast =” auto “> will balance span >< span data – contrast =” auto “> the market span >< span data – contrast =” auto “>  out . span >

< span data – contrast =” auto “>“ Smart metering and a half – hourly tariff is absolutely a key enabler . I think the consumers are going to want to understand what what ‘ s in it for them , and what ‘ s the benefit for them to switch . In the home , they ’ ve been enabled by smart devices . span >

< span data – contrast =” auto “>“ I can press the button on the dishwasher , and it knows that I just need to have clean dishes in the next 10 hours . It works out when in the next 10 hours is the optimum time to start , either from a cost perspective or a carbon intensity perspective . The technology is already laid out , you just need incentive to buy it .” span >

The future energy profile of the UK transmission system

< span data – contrast =” auto “> These new technologies offer the biggest change for grid balancers worldwide , as   domestic consumers   become more responsive in their power demands . Leslie said : “ Today , we dispatch generation to meet the demand curve , because historically , the generation is the part we can control . The   big change   is   in   making demand something we can control , because we ‘ ll have 10 million electric vehicles and many homes will have batteries . span >

[ caption id =” attachment_134382 ” align =” aligncenter ” width =” 620 “]< img class =” wp – image – 134382 ” src =” https :// www . power – technology . com / wp – content / uploads / sites / 7 / 2021 / 05 / CreditNationalGrid – Pylon – Maintenance – South – Wales – PR – High – Res – 450×340 . jpg ” alt =” Pylon maintenance works ” width =” 620 ” height =” 413 ” /> Physical transmission infrastructure in the UK is owned and operated by separate companies . Credit : National Grid .[/ caption ]

< span data – contrast =” auto “>“ You could say this will flatten and suppress the peaks , I absolutely think that will happen . But equally , a peak could occur at four o ‘ clock on a Sunday morning , because that ’ s when the wind is blowing the strongest and everybody ‘ s charging their vehicles , getting their hot water and heating ready , and getting some store of energy to heat their oven to cook their Sunday roast . span >

< span data – contrast =” auto “>“ span >< span data – contrast =” auto “> I think it ‘ s not so much a flattening of the curve , it ‘ s about matching the demand with when the generation span >< span data – contrast =” auto “>  i span >< span data – contrast =” auto “> s available .” span >

< span data – contrast =” auto “> Leslie believes there   is still   a ‘ long way to go ’ before weekday transmission demand starts   looking similar to that of the weekend .  He says : “ The demand shape will shift through other means , as we look to the future . Things like smart tariffs , and people being encouraged to consume energy when the sun is high , the wind is blowing in the right direction , and the demand is low .” span >

< em > Read about the changing profile of grid balancing in our article on half-hourly settlement. em >