Could you be the Wind God?

Scenario: You have been appointed the UK Government's minister responsible for smoothing out the intermittent output from renewable wind and solar PV electricity generation. You're going to do this by specifying storage technology that can store and release power according to variations in supply, rather than relying on coal and gas power stations stopping and starting to balance the grid. Your policy will then be tested against actual 2019 daily data provided courtesy of GRIDWATCH

Unofficially your job title is THE WIND GOD

Minister, we now need you to make some policy decisions, including the total storage capacity (in MW-h) and its instantaneous power rating (in MW). The storage facility (or facilities) can either consume power to charge the storage or generate power, as the storage is discharged. For example if you specified 144,000 MW-h of storage and a 2,000 MW power rating, that is 3 days storage full-to-empty (2,000 MW x 24 h/d x 3 d)

The average power output from wind and solar PV is 6700 MW - and we'd like you to treat that as a target - but it won't be easy.

In 2019, minimum output has been as low as 1,000 MW, maximum in excess of 12,000 MW. On days when wind and solar PV power exceeds the target, the excess will be automatically put into storage, up to the maximum power rating you specified - and provided there is spare capacity in the store. On days when wind and solar PV power is below the target, power will be drawn automatically from storage, again up to the maximum power rating, on condition the store is not completely depleted at the time.

However much storage you allocate, we'll ensure it is 50% charged at the start of day 1 (January 1st 2019)

What power rating should the system have in MW?
And how much storage should be allocated in MW-h?

Your assessment, minister: Net output was 1000 MW or more over the target on 51 days out of 212. On such days we would have to pay generators to shut down operation. Net output fell 1000 MW or more under target on 47 days out of 212 and on these days we would have to purchase standby power most likely using fossil fuel. Your proposed storage would require 5 Coire Glas scale storage schemes at an estimated cost of £4 billion

Overall, we'd rate your performance at 39 % - we're a bit dissapointed with that result, Minister. Here are the full results:

2019WindSolarWind+SolarIn/OutReserveNet W+S
Day:MWMWMWMWMW-hMW
162637016964200768006764
221424962638-2000288004638
313663521718-120002918
424027053107003107
52688852773002773
616513001951001951
710257230104872000480008487
893001000103002000960008300
9420310765279-1400624006679
1032552493504-2000144005504
1149843535337-60005937
1210868214110822000480009082
1310642418110602000960009060
14636463369972001008006797
1598425011034318001440008543
168810254906401440009064
1768641583844701440008447
186011651666201440006662
1938794394318-2000960006318
20181510342849-2000480004849
2149908645854-800288006654
2243399665305-120006505
23163411232757002757
246913671058001058
25905170497552000480007755
26929347697692000960007769
2799258481077320001440008773
2860671822788901440007889
2944843924876-18001008006676
30239816244022-2000528006022
3130008533853-200048005853
3249097105619-20005819
3353281672700020048006800
34581014997309600192006709
35744979882471400528006847
3657693176086-600384006686
37641710807497600528006897
3875371693923020001008007230
39112104681167818001440009878
409806142911235014400011235
4152779016178-4001344006578
42263415694203-2000864006203
437907940884720001344006847
448553138999424001440009542
4555071970747701440007477
4667882774956201440009562
477962796875801440008758
489892149911391014400011391
49945794310400014400010400
5070181714873201440008732
519162103010192014400010192
5262061583778901440007789
5363552217857201440008572
5463022050835201440008352
55234828685216-14001104006616
56210528594964-1600720006564
57178932044993-1600336006593
58106629424008-140005408
5918808112691002691
6019788122790002790
617560108686461800432006846
62840449188952000912006895
63947118011127220001392009272
646329233686652001440008465
658759731949001440009490
669772134311115014400011115
6767401230797001440007970
688970248211452014400011452
6973452042938701440009387
709356315212508014400012508
71999674510741014400010741
7210207186912076014400012076
739871210611977014400011977
749431139310824014400010824
758228656888401440008884
769175230111476014400011476
77236517804145-2000960006145
78388415935477-1200672006677
794947165666030672006603
80343313394772-1800240006572
8166767697445600384006845
82424721086355-200336006555
8371753378105532000816008553
8461863453963920001296007639
85403522586293-4001200006693
86387218405712-8001008006512
87373326706403-200960006603
883860322870882001008006888
89237122904661-2000528006661
90420421076311-200480006511
915045272477691000720006769
92270617124418-2000240006418
93445919276386-200192006586
947308137186791800624006879
9576101604921420001104007214
96303320235056-1600720006656
97384214865328-1200432006528
98402320896112-400336006512
99570815817289400432006889
1003571328768580432006858
101206235485610-1000192006610
102410123386439-200144006639
10368653246101112000624008111
104810622751038120001104008381
1058740343712177140014400010777
10652041593679701440006797
10737113233694401440006944
10849403376831601440008316
10932493802705101440007051
110177533865161-14001104006561
111307333166389-2001056006589
11252252989821414001392006814
1135884216780512001440007851
11461211985810601440008106
11556731859753201440007532
11676402073971301440009713
11779861930991601440009916
118330119915292-14001104006692
119120622343440-2000624005440
120107026983768-2000144005768
12156317392302-60002902
122258320284611004611
123355613734929004929
12474422992104342000480008434
1254351225566060480006606
126163823864024-200006024
127112321523275003275
1286841120980501200288006850
129317215344706-120005906
13068224333115003115
131182527354560004560
13279634714267004267
133142035764996004996
134143238385270005270
135185834715329005329
1364936320981451400336006745
137372214765198-140006598
13896516792644002644
13965820672725002725
140136726454012004012
141184035265366005366
142255620064562004562
143405933207379600144006779
144335327876140-40048006540
145185827514609-20004809
1467282186291442000480007144
147380622956101-400384006501
148204824224470-160006070
149389515835478005478
1506864238092442000480007244
1515878198878661000720006866
152316928826051-600576006651
15371972140933720001056007337
15468632877974016001440008140
155247015434013-2000960006013
156312621525278-1400624006678
157221931255344-1200336006544
158474413696113-400240006513
1596429188083091600624006709
160191725674484-2000144006484
161262014144034-60004634
1626215952716740096006767
16362579997256400192006856
164632711017428600336006828
165408622466332-200288006532
166391221416053-600144006653
167484823487196400240006796
1686334246387972000720006797
169334319335276-1400384006676
170158618353421-160005021
171384426266470006470
172244128085249005249
173152733044831004831
174447417276201006201
175295016384588004588
176361712234840004840
177365619825638005638
178358337457328600144006728
1794654326179151200432006715
180317130406211-400336006611
18184352769112042000816009204
182812423971052120001296008521
183371925546273-4001200006673
184262434946118-4001104006518
1854179349076698001296006869
186347329976470-2001248006670
187290719644871-1800816006671
188162926754304-2000336006304
189104327013744-140005144
190109717352832002832
191153325804113004113
192165325274180004180
193335629126268006268
194314821615309005309
195187221203992003992
19685624973353003353
19768127463427003427
198379221325924005924
199357622095785005785
200398210605042005042
2015566240279681200288006768
202494324137356600432006756
20381582402105602000912008560
2044315299873136001056006713
20540872643673001056006730
2064912268475968001248006796
207315115764727-1800816006527
208291510994014-2000336006014
209397214085380-120048006580
210210425744678-20004878
211429114585749005749
212584516247469600144006869