ANALYSIS OF A MULTI-DAY WIND/SOLAR LULL DURING WINTER IN NEW ENGLAND

Based on the plan of eliminating fossil fuel plants (they emit CO2 and particulates) and nuclear fuel plants (they are alleged to be dangerous) by 2050, the existing gas, nuclear, coal and oil generating plants would be decommissioned and no new ones would be built.

 

This would require huge build-outs of wind, solar, and storage systems, and increased electricity supply via external ties to adjacent grids.

 

The storage systems serve to cover wind and solar lulls, which occur at random throughout the year, and seasonal variations. There is no way one can close down nuclear, oil, gas and coal plants and not replace them with energy storage systems.

 

http://www.windtaskforce.org/profiles/blogs/wind-plus-solar-plus-st...
http://www.windtaskforce.org/profiles/blogs/wind-and-solar-energy-l...

http://www.windtaskforce.org/profiles/blogs/world-coal-consumption-...

Wind and Solar Lulls are Frequent Occurrences During Winter

 

Often the combined output of wind plus solar is at near-zero levels during many hours of the year. See URL, click on Renewables. In the Fuel Mix Chart, refreshed every 15 minutes, you will see the instantaneous wind and solar percent in New England. 

http://www.iso-ne.com/isoexpress/

 

The ISO-NE spreadsheet in the URL shows daily generation of wind and solar during January 2017. Solar output was 508 MWh and wind was 1,987 MWh on 20 January 2017. During that day, wind and solar varied from minute to minute, with some hours at near zero.

https://www.iso-ne.com/isoexpress/web/reports/operations/-/tree/dai...

 

NOTE: During the year the totals of wind and solar, MWh, were: Jan 20, 2496; Mar 28, 1950; Sep 18, 2529; Nov 13, 1753; Dec 3, 2157; Dec 9, 2458, i.e., minimal wind and solar are frequent occurrences.

 

During the Dec 24, 2017 - Jan 9, 2018 cold spell (15 days), wind output was less than 100 MW 6 times, from the 1300 MW of wind turbine capacity monitored by ISO-NE. See page 50 in URL.

 

During the cold spell, solar output, after the meter (larger, field-mounted, etc.), was less than 500 MW 13 times, from the installed 2350 MW. See page 48 of URL.

 

During the cold spell, solar output, in front of the meter (residential roof top, etc.), was less than 10 MW 9 times, from the installed 83 MW. See page 49 of URL

https://www.iso-ne.com/static-assets/documents/2018/01/20180112_col...

 

Increased Electricity Supply Via External Ties

 

Hydro-Quebec Building New Plants, Upgrading Others: Below items 1 through 4 would enable H-Q to have at least 5000 MW x 8766 x 0.60 = 26,298,000 MWh/y, or 26.3 TWh, for export via new power lines that are being proposed, in addition to existing exports. If that electricity were not there, would various private entities propose HVDC power lines worth billions of dollars?

 

1) Hydro-Québec Production obtained the necessary approvals to build a 1,550-MW hydroelectric complex on the Rivière Romaine, north of the municipality of Havre-Saint-Pierre on the north shore of the St. Lawrence. The complex will consist of four hydro plants, Romaine 1, 2, 3 and 4, with total average output of 8.0 TWh/y; CF 0.60.

 

2) Other power plants up north are being refurbished (better water flow) and being upgraded with more efficient turbines, i.e., will produce more electricity.

 

3) Existing plants not being fully utilized (water over the spillways instead of through the turbines, especially in summer).

 

4) H-Q building future hydro plants and wind systems.

 

Quebec, New Brunswick and New York supply about 20.8 million MWh/y of electricity to the NE grid. See table 3.

 

With additional HVDC transmission lines, the above 4 items likely would enable an external tie supply of about 2 x 20.8 = 41.6 million MWh/y by 2050.

 

Electricity Alternatives in 2050: The following alternatives were analyzed:

 

Alternative 1

- No gas, nuclear, coal and oil generating plants

- Major build-outs of wind, solar, hydro, refuse, and battery systems

- No increase in supply via external ties

 

The calculated capacity of the storage system was based on:

 

- Wind and solar generation increased to 10 times existing, or (508 +1987) x 10 = 24,960 MWh.

- Refuse (municipal waste) generation increased to 5 times existing.

- Wood generation not increased, because it is already harvested near 50% of net biomass growth.

- NE hydro generation increased by about 20%, mostly by upgrading existing plants.

- External ties remain unchanged.

 

Alternative 2

- No gas, nuclear, coal and oil generating plants

- Much less build-outs of wind, solar and battery systems

- Significant increase in supply via external ties

 

The calculated capacity of the storage system was based on:

 

- Wind and solar generation increased to 6 times existing, or (508 +1987) x 6 = 14,976 MWh.

- Refuse (municipal waste) generation increased to 5 times existing.

- Wood generation not increased, because it is already harvested near 50% of net biomass growth.

- NE hydro generation increased by about 20%, mostly by upgrading existing plants.

- External ties increased to 2 times existing.

 

Summary of Turnkey Capital Cost of Alternatives:

 

Table 1 shows the capital costs for the two alternatives for:

- A 1-day wind and solar lull

- A 4-day lull

- 2 consecutive 4-day lulls.

 

Alt. 1 shows, the battery cost would be about $260 billion, at $250/kWh delivered as AC.

Alt. 2 shows, the battery cost would be about $166 billion, at $250/kWh delivered as AC.

A significant percentage of the battery capital cost would be repeated every 15 years to replace the batteries.

 

Tables 4 and 6 have more detail.

 

Table 1	Alt. 1	Alt. 1	Alt. 1	Alt. 2	Alt. 2	Alt.2
Wind and Solar Lull	1 day lull	4-day lull	(2) 4-day Lulls	1-day lull	4-day lull	(2) 4-day lulls
	$billion	$billion	$billion	$billion	$billion	$billion
Capacity build-out	100.15	100.15	100.15	69.68	69.68	69.68
Grid expansion	15.02	15.02	15.02	10.45	10.45	10.45
Total	115.17	115.17	115.17	80.13	80.13	80.13
Transmission to Canada	0	0	0	15.02	15.02	15.02
NE Storage; $250/kWh	32.47	129.87	259.73	20.71	82.85	165.71
Total	147.64	245.04	374.90	115.87	178.00	260.86

 

Summary of Battery Capacities of Alternatives

Batteries are rated to discharge at a power level, MW, for a period of hours. The correct way of stating a battery rating 1 MW / 4 MWh of delivered AC. Prices should be stated as $/kWh of delivered AC.

 

For analysis purposes, it was assumed:

 

AC to DC conversion and charging efficiency is 0.93

DC to AC conversion and discharging efficiency is 0.93

AC to AC round-trip efficiency is 0.93 x 0.93 = 0.865; round-trip efficiencies vary with the type of battery.

 

A battery system typically is not charged to more than 95% and not discharged to less than 25%, to ensure longer battery life, i.e., a maximum of 70% of the stored charge is available.

 

For 1.04 TWh delivered as AC to the HV grid, the stored charge would need to be about 1.04/(0.93 x 0.70) = 1.6 TWh.

 

Additional build-outs of generating plants (wind, solar, bio, hydro, etc.) are required to offset the round-trip losses when storage systems are a part of the electric grid.

 

Storage systems can provide services that generate revenues, but those revenues are just a small return on the invested capital cost, if all O&M, financing, and subsidy costs are properly accounted for, which usually is not the case. See URLs and APPENDIX 10.

 

http://www.windtaskforce.org/profiles/blogs/high-costs-of-wind-and-...
http://www.windtaskforce.org/profiles/blogs/pv-solar-sonnen-combo-l...

  

Table 2	Alt. 1	Alt. 1	Alt. 1	Alt. 2	Alt. 2	Alt.2
Wind and Solar Lull	1-day lull	4-day lull	(2) 4-day Lulls	1-day lull	4-day lull	(2) 4-day Lulls
	MWh	MWh	MWh	MWh	MWh	MWh
Delivered as AC	129865	519460	1038920	82854	331416	662832

 

Generation and Load of New England Grid in 2016, per ISO-NE Data

 

About 84.9% of the NE system load is generated from various sources in New England. See table 3.

 

Table 3/2016 ISO-NE data	Generation	Generation	System Load	Generation
	GWh	%	GWh	% of system load
Total Generation	105572	100.0	124416	84.9
Gas	52059	49.3	52059	41.8
Nuclear	32745	31	32745	26.3
Renewables	10231	9.7	10231	8.2
- Refuse	3316	3.1	3316	2.7
- Wood	3200	3	3200	2.6
- Wind	2519	2.4	2519	2.0
- Solar	658	0.6	658	0.5
- Landfill Gas	496	0.5	496	0.4
- Methane	42	0.04	42	0.0
Steam	0	0	0	0.0
Hydro	7465	7.1	7465	6.0
Coal	2555	2.4	2555	2.1
Oil	517	0.5	517	0.4
Other (c)	0	0	0	0.0
Net Flow over External Ties			20803	16.7
- Québec			12285	9.9
- New Brunswick			4842	3.9
- New York			3675	3.0
Pumping Load			-1959	-1.6
Net Energy for Load		100.0	124416	100.0

 

Alternative 1

 

Turnkey Capital Cost: Table 5 shows an estimate of the capital cost required for the build-outs, including grid augmentation and expansion, and storage for a 1-day lull.

 

Table 4/Capital Cost	Existing	Added	Total		Cost
	MW	MW	MW	$million/MW	$billion
Wind	1377	12393	13770	2.5	30.98
Solar	1918	17262	19180	3.5	60.42
Refuse	540	2160	2700	3.5	7.56
Hydro	1703	341	2044	3.5	1.19
					100.15
Grid expansion				0.15	15.02
					115.17
Transmission to Canada					0.00
Storage					32.47
Turnkey capital cost					147.64

Turnkey Capital Cost of Storage Systems:

 

Table 5	20-Jan-17	Factor	Future
Source	Load		Generation
	MWh		MWh
Gas	136322		0
Nuclear	96491		0
Refuse	19540	5	97700
Wood	8767	1	8767
Wind	1987	10	19870
Solar	509	10	5090
NE Hydro	25899	1.2	31079
Coal	2766		0
Oil	90		0
Other	40	1	40
External ties	56995	1	56995
Pumping load	-5367	1	-5367
Total	344039		214174
Shortfall from storage, MWh as AC			129865
$/kWh as AC; See Note			250
Turnkey capital cost; $billion			32.47

 

Alternative 2

 

Based on ISO-NE generation and load data for 2016, the storage capacity to cover seasonal variations would be about 8 TWh, delivered as AC to the HV grid. Generation from all sources would be stored in the battery systems. Based on the above-assumed generation, the system would be:

 

- Charged at about 3 TWh at the start of January

- Charged at about 8 TWh at the end of May

- Fully discharged at the end of September

- Charged at about 3 TWh from the start of December to the end of January

 

1) Generation from all sources have to cover demand, plus provide electricity due to storage losses.

2) Items 2 and 3 would be on a 24/7/365 basis.

3) The storage system would provide the peaking, filling-in and balancing services.

Turnkey Capital Cost: Table 7 shows an estimate of the capital cost required for the build-outs, including grid augmentation and expansion, and storage for a 1-day lull.

 

Table 6/Capital Cost	Existing	Added	Total		Cost
	MW	MW	MW	$million/MW	$billion
Wind	1377	6885	8262	2.5	20.66
Solar	1918	7672	11508	3.5	40.28
Refuse	540	2160	2700	3.5	7.56
Hydro	1703	341	2044	3.5	1.19
					69.68
Grid expansion				0.15	10.45
					80.14
Transmission to Canada					15.02
Storage					20.71
Turnkey capital cost					115.87

 

Turnkey Capital Cost of Storage Systems:

 

Table 7	20-Jan-17	Factor	Future
Source	Load		Generation
	MWh		MWh
Gas	136322		0
Nuclear	96491		0
Refuse	19540	5	97700
Wood	8767	1	8767
Wind	1987	6	11922
Solar	509	6	3054
NE Hydro	25899	1.2	31079
Coal	2766		0
Oil	90		0
Other	40	1	40
Net Flow over External Ties	56995	2	113990
Pumping Load	-5367	1	-5367
Total	344039		261185
Shortfall from storage, MWh as AC			82854
$/kWh as AC			250
Turnkey capital cost; $billion			20.71

 

APPENDIX 1

Wind and Solar Energy Lulls and Energy Storage in Germany: This article describes in detail the storage requirements to cover a 100-hour wind and solar lull, followed by a 50-hour lull a few days later during the winter. This requires the availability of:

 

- Enough electricity generation (wind, solar, hydro, wood, refuse, etc.) to recharge the battery systems in a few days, including charging losses of about 10%, plus serve the demand (a very tall order), or

- An even greater battery storage capacity to serve demand during the 2nd lull, or

- A significant, not weather-dependent, gas-fired, CCGT plant capacity, MW.

 

Also note:

- The battery systems likely would not be fully charged at the onset of any wind and solar lull.

- The safe approach would be to have available the additional storage capacity for a second lull, or the CCGTs.

http://www.windtaskforce.org/profiles/blogs/wind-and-solar-energy-l...

 

APPENDIX 2

- Source energy is the energy taken from coalmines, oil and gas wells, and forests for conversion to electricity and heat.

- Primary energy = source energy - energy used for exploration, extraction, processing and transport of fuels (coal, oil, gas, biofuels, wastes, etc.) to users, such as fuel to electricity generating plants, or process plants, or buildings, or vehicles, etc. That means it has not been subjected to any conversion or transformation process.

http://www.windtaskforce.org/profiles/blogs/source-energy-and-prima...

 

APPENDIX 3

The Jacobson WWS Studies: Jacobson, an environmental professor at Stamford University, California, performed several WWS studies of which one of them claimed all of US primary energy could be provided by “Wind, Water and Solar” by 2050.

 

Because of the weather dependency and seasonality of wind and solar, huge quantities of stored electricity are required. The stored electricity must be immediately made available all over the US, as needed by demand, 24/7/365.

 

He relied mainly on the thermal storage of concentrated solar power, CSP, systems in the US southwest. The stored electricity would be distributed to the rest of the US, via a US-wide, HVDC overlay grid (a $400 billion system), connected at many points to the existing HVAC grids. See URL.

http://www.windtaskforce.org/profiles/blogs/review-of-the-100-re-by... 

 

APPENDIX 4

Historic Build-Out of Wind Capacity in New England: Annual additions of wind turbine build-outs varied from about 139.3 MW in 2009 to 339 MW in 2016.

 

If a 300 MW build-out rate were maintained for the next 10 years, then 1377, existing + 3000, new = 4379 MW would be installed by 2026.

 

It would take about 4 decades to implement Alternative 1, which assumes 1377 x 10 = 13770 MW would be installed at some future date.

https://windexchange.energy.gov/maps-data/321

 

Table 8	VT	ME	NH	MA	RI	CT	NE	Y to Y
Year	MW	MW	MW	MW	MW	MW	MW	MW
2000	6.1	0.1	0.1	0.3	0.0	0.0	6.6
2001	6.1	0.1	0.1	1.0	0.0	0.0	7.3	0.7
2002	6.1	0.1	0.1	1.0	0.0	0.0	7.3	0.0
2003	6.1	0.1	0.1	1.0	0.0	0.0	7.3	0.0
2004	6.1	0.1	0.1	1.0	0.0	0.0	7.3	0.0
2005	6.1	0.1	0.1	1.0	0.0	0.0	7.3	0.0
2006	6.1	9.1	1.1	3.5	0.7	0.0	20.5	13.2
2007	6.1	42.1	1.1	5.0	0.7	0.0	55.0	34.5
2008	6.1	46.6	25.1	5.7	0.7	0.0	84.2	29.2
2009	6.2	174.7	25.2	15.0	2.4	0.0	223.5	139.3
2010	6.2	266.2	25.5	17.7	2.4	0.0	318.0	94.5
2011	46.0	397.0	26.0	47.0	2.0	0.0	518.0	200.0
2012	119.0	431.0	171.0	103.0	9.0	0.0	833.0	315.0
2013	119.0	431.0	171.0	106.0	9.0	0.0	836.0	3.0
2014	119.0	440.0	171.0	107.0	9.0	0.0	846.0	10.0
2015	119.0	613.0	185.0	107.0	9.0	5.0	1038.0	192.0
2016	119.0	901.0	185.0	115.0	52.0	5.0	1377.0	339.0
2017	149.0	923.0	185.0	115.0	54.0	5.0	1431.0	54.0
2018	149.0	923.0	185.0	113.0	75.0	5.0	1450.0	19.0
2019	149.0	923.0	185.0	113.0	75.0	5.0	1450.0	0.0

APPENDIX 5

Wind and Solar Conditions in New England: New England has highly variable weather and low-medium quality wind and solar conditions. See NREL wind map and NREL solar map.

https://www.nrel.gov/gis/images/100m_wind/awstwspd100onoff3-1.jpg

https://www.nrel.gov/gis/images/solar/national_photovoltaic_2009-01...

 

Wind:

- Wind electricity is zero about 30% of the hours of the year (it takes a wind speed of about 7 mph to start the rotors)

- It is minimal most early mornings and most late afternoons/early evenings (peak demand hours), especially during summer

- About 60% is generated at night, when demand is much less than during the late afternoons/early evenings

- About 60% is generated in winter.

- During winter, the best wind month is up to 2.5 times the worst summer month

- New England has the lowest capacity factor (about 0.262) of any region in the US, except the US South. See URL.

https://www.eia.gov/todayinenergy/detail.php?id=20112

 

Solar:

- Solar electricity is strictly a midday affair.

- It is zero about 65% of the hours of the year

- It is always minimal early mornings and late afternoons/early evenings

- It is minimal much of the winter

- It is near zero with snow and ice on the panels.

- It varies with variable cloudiness, which would excessively disturb distribution grids with many solar systems, as happens in southern California and southern Germany on a daily basis. See Note.

- During summer, the best solar month is up to 4 times the worst winter month; that ratio is 6 in Germany.

- New England has the lowest capacity factor (about 0.145, under ideal conditions) of any region in the US, except some parts of the US Northwest.

 

If we were to rely on wind and solar for most of our electricity, massive energy storage systems (GWh-scale in case of Vermont) would be required to cover multi-day wind lulls, multi-day overcast/snowy periods, and seasonal variations. See URL.

http://www.windtaskforce.org/profiles/blogs/wind-and-solar-energy-l...

 

APPENDIX 6

Table 2 shows the loads, GWh, on the New England electric grid for the 2000 - 2016 period, as seen by ISO-NE. There is a tiny quantity of “before the meter” generation, such as residential rooftop solar, which is not seen by ISO-NE.

 

There has been no load growth for since 2010, due to energy efficiency measures and a small quantity of before the meter generation used by owners of rooftop solar systems, such as residences.

https://www.iso-ne.com/isoexpress/web/reports/operations/-/tree/net...

 

Table 9/Year	ISO-NE Load	NE Generation	Imports
	GWh	GWh	GWh
2000	125,394	110,195	15,199
2001	126,484	114,626	11,858
2002	128,027	120,539	7,488
2003	130,776	127,195	3,581
2004	132,517	129,459	3,058
2005	136,355	131,877	4,478
2006	132,087	128,050	4,037
2007	134,466	130,723	3,743
2008	131,754	124,749	7,005
2009	126,838	119,437	7,401
2010	130,773	126,416	4,357
2011	129,163	120,610	8,553
2012	128,081	116,942	11,139
2013	129,377	112,041	17,336
2014	127,189	108,357	18,832
2015	126,955	107,916	19,039
2016	124,416	105,570	18,846

 

APPENDIX 7

Cancellation of Offshore Wind Turbine Plant: As is well known by now, Cape Wind, 468 MW, started in 2001, turnkey capital cost $2.6 billion, $5550/kW, to be located south of Nantucket, highly visible to many multi-millionaires summering on the Island, has finally been cancelled as of 1 December 2017. See URLs.

 

http://www.windtaskforce.org/profiles/blogs/cape-wind-cancelled-as-...

http://www.windtaskforce.org/profiles/blogs/a-very-expensive-offsho...

 

The negotiated Cape Wind power purchase agreement, PPA, called for 18.7 c/kWh the first year, increasing at 3.5% per year for 20 years, to reach 37.2 c/kWh in the 20th year. These are the prices at which the variable, intermittent electricity would be sold to a utility. See URL.

http://www.windtaskforce.org/profiles/blogs/the-true-cost-of-wind-e...

 

NOTE: New England wholesale prices have averaged about 5 c/kWh for steady, 24/7/365 electricity since about 2008, primarily due to:

 

- Natural gas; 50% of NE generation; low-cost (less than 5 c/kWh), low-CO2 emitting, no particulates, domestic fuel 

- Nuclear; 26% of NE generation; low-cost (less than 5 c/kWh), minimal-CO2 emitting, no particulates, domestic fuel

https://www.bloomberg.com/news/articles/2017-12-01/cape-wind-develo...

 

NOTE: Purposely, I did not consider any build-outs of offshore wind, as that electricity generation would have been at least 2 times more costly than from 2000 ft.-high ridgelines. It would have made worse an already bad situation. See URL.

http://www.windtaskforce.org/profiles/blogs/cop21-flawed-trade-agre...

 

APPENDIX 8

Wind and Solar Capacity at End 2016: Table 1 shows the installed wind and solar capacity and generation at end 2016. The solar is before and after the meter.

- The generation by wind is greater than in table 1, because a CF = 0.262 was used, and it was assumed all wind turbines were operated the entire year.

- The generation by solar is greater than in table 1, because a CF = 0.145 was used, and it was assumed all solar systems were operated the entire year.

 

Table 10/Year	Capacity	Generation	% of NE generation
2016	Installed MW	MWh
NE Wind	1377	3,162,544	3.0
NE Solar	1918	2,353,846	2.2

 

APPENDIX 9 

If a lithium-ion battery is rated at 1 MW/4 MWh AC, it means it can deliver 1 MW of AC power for 4 hours.

The battery would be charged to 95% of capacity and discharge to 25% of capacity, for a total range of 70%, to preserve life. This is a typical practice of EV manufacturers. Usually, batteries have a maximum discharge of 50% or less for long life. The loss of one charge/discharge cycle is 100 x (1 – 4/4.62) = 13.51%

 

Table 11/Battery Charging and Discharging		MWh
Discharge mode
Delivered as AC		4.00
Discharge loss	%	7
From battery storage as DC	4/0.93	4.30
Discharge loss from battery storage as DC	4.30 – 4.00	0.30
Stored in battery before discharge as DC	4.30/0.7	6.14
Stored in battery after discharge as DC	6.16 – 4.30	1.84
Charge mode
Charge loss	%	7
From meter to charge battery as AC	4.30/0.93	4.62
Charge loss as DC	4.62 x 0.07	0.32
Stored into battery as DC	4.62 – 0.32	4.30
Initial charge as DC		1.84
Final charge as DC	4.30 + 1.84	6.14
Charge/Discharge cycle loss, %	100 x (1 – 4.00/4.62)	13.51

APPENDIX 10 

100% RE folks often talk about wind and solar being so competitive with fossil and nuclear. Those RE folks likely have near-zero experience designing energy systems, but pontificate anyway, and get listened to by legislators and bureaucrats. What 100% RE folks do not mention is the various costs charged to the public, which make wind and solar appear less costly/kWh than in reality:

1) The cost of storage systems required for accommodating the variability and intermittency of wind and solar.

2) The cost of transmission expansions and enhancements

3) Direct subsidies (cash grants, rapid depreciation, low-cost loans, etc.) to generator owners, which enable them to bid on electricity supply contracts at prices that appear competitive with fossil fuels, hydro and nuclear.

 

http://www.theenergycollective.com/energy-innovation-llc/2420282/ra...

http://www.windtaskforce.org/profiles/blogs/subsidized-solar-system...

http://www.windtaskforce.org/profiles/blogs/the-true-cost-of-solar-...

http://www.windtaskforce.org/profiles/blogs/the-true-cost-of-wind-e...

http://www.windtaskforce.org/profiles/blogs/a-very-expensive-offsho...

APPENDIX 11

New England Will Have Brownouts and Higher Electricity Prices: During the bitter cold stretch that started right after Christmas and continued into 2018, ISO-NE had a tough time keeping the electricity flowing to homes and businesses throughout New England.

 

Facing a shortage of natural gas because of a dearth of pipeline capacity, they relied on old oil and coal plants to provide enough electricity.

 

With oil supplies rapidly running low, ISO-NE, responsible for ensuring the region’s electricity supply, said keeping the whole system up and running proved “extremely challenging” as operators “worked around the clock to keep the power flowing and the grid stable.”

http://www.sunjournal.com/maine-may-face-brownouts-higher-electric-...

 

APPENDIX 12

Vermont Example of Electricity Storage With Tesla Powerwall 2.0s: Vermont supply to grid, as measured by ISO-NE = 6,100,000 MWh/y, or 16,712,329 kWh/d.

A fully charged Powerwall delivers 13.5 kWh

Powerwalls required = 16,712,239/13.5 = 1,237,950 for one day of electricity, or 4,951,801 units for 4 days.

Covering a 4-day wind lull in winter (solar likely would be minimal as well) would require 4 x 4,951,801 x $6000 = $29.7 billion

NOTE: A less costly alternative would be 4 days x 130 Tesla's 100MW/129MWh Powerpack systems at $20.7 billion. The 520 systems would be spread throughout Vermont.

Tesla/GMP would love to sell all those batteries.

The Powerwalls have a useful life of about 10 – 12 years and likely would be returned to Tesla for “processing”. The cost/kWh of that approach would be expensive.

After the 4-day wind lull, it would need to be windy for some days to provide electric service and recharge the Powerwalls, which would need to be ready for the next wind lull; all that time solar likely would be minimal during winter hours.

Wind turbines required to serve demand and refill batteries, if another 4-day lull occurs 6 days later = {(6 x 16,712,329, normal demand) + (1.2, round-trip factor x 4,951,801 x 13.5, fill batteries)}/144 h x 0.30 CF = 4178 MW, say 4200 MW.

Cost: Turbines $12.6 billion, at $3 million/MW, plus grid $1.3 billion = $13.9 billion.

Vestas, Iberdrola, GE would love to sell all those turbines.

NOTE: Hydro-Quebec hydro, unwisely rejected by GMP, et al., and Vermont Yankee nuclear, unwisely hounded to close down, would have provided clean, near-CO2-free, low-cost (5-6 c/kWh), steady (not variable/not intermittent), electricity, 24/7/365, FOR ALMOST ALL OF VERMONT, sun or no sun, wind or no wind.

The H-Q approach would require minimal investments for transmission, and no subsidies, no ruined ridge lines, and would not further ruin the anemic, near-zero, real-growth Vermont Economy.

http://provisionsolar.com/wp-content/uploads/2016/12/Powerwall-2_AC...