MORE REALISTIC ENERGY SOURCE FACTORS

This article deals with the energy from source to electrical energy user. The complete pathway must be used to enable evaluation of one energy pathway versus another. First some definitions:

 

- Source energy is the energy taken from coal mines, 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.

- Consumed energy by users = net electricity generation (fed to grid)  + fuel to process plants, or buildings, or vehicles, etc.

- Gross electricity generation = primary energy (fuel to power plants) x plant efficiency.

- Net electricity generation = fed to grid = gross generation - plant self-use. 

- Electricity at user meters = fed to grid - transmission & distribution losses.

 

NOTE: VT Energy Action Network assumes the source factors (source energy/energy delivered to grid) of wind, solar and hydro as 1.0; NE grid energy 2.63; nuclear 3.08; and biomass 3.33, which ignores T&D losses, and ignores the efficiency losses of the other generators performing the peaking, filling-in and balancing the variable wind and solar energy. It does not enable the evaluation of one energy pathway versus another. The below energy pathway calculations include those losses.

Plant Self-Use

Traditional power plants feed about 95% of their gross generation to the grid and use about 5% for running the plant (self-use). The percentage varies with the type of plant; for a gas plant the percentage is less, for a coal and wood plant the percentage is greater.

Transmission and Distribution Losses

 The EIA estimates US T&D losses at about 5%. However, for mostly rural states, such as Vermont, the percentage is significantly greater. about 9 to 10 percent, according to the Utility Facts report, prepared by the Department of Public Service (DPS); the data are as shown in the table. For this article, T&D losses were assumed at 7%.

http://publicservice.vermont.gov/sites/dps/files/documents/Pubs_Pla...

 

Year	2010	%
GMP sales	4,309,643 MWh	77.0
Other utilities sales	1,285,157 MWh	23.0
Total sales	5,594,800 MWh	100.0
Total utility purchases	6,188,000 MWh
T & D loss	593,200 MWh	9.6

 

Embodied Energy

The source energy required for building the plant, and operating and maintaining it in good operating condition usually is not separately stated, because:

 

- Traditional power plants (gas, coal, nuclear, hydro, wood) have high capacity factors (0.60 to 0.90) and long lives (40 to 60 years). Their embodied source energy is low per MWh.

- Wind and solar power plants have low capacity factors (0.25 to 0.40) and short lives (about 25 years). Their embodied source energy is high per MWh. See below examples.

 

Wood Source Energy Factor (power plants)

Losses = Upstream (harvest, chipping, transport (2.5%) + Conversion to electricity, including site self-use (75%) + Transmission and distribution (7%) = 84.5%, i.e., 15.5% arrives at the user meters.

 

The source energy factor for wood power plants is 100/15.5 = 6.45, i.e., the energy equivalent of 5.45 of 6.45 trees is wasted. That value is much higher than the 3.33 assumed by Energy Action Network for only a part of the energy pathway.

 

Wood Source Energy Factor	%
Upstream (harvest, chipping, transport)	2.5
Conversion to electricity, including site self-use	75.0
Transmission and distribution	7.0
Total loss	84.5
Arriving at user meters	15.5
Source energy factor 100/15.5	6.45

 

McNeil and Ryegate are Major Pollution Sources

McNeil and Ryegate wood-fired power plants emit much more pollutants/MWh and much more CO2/MWh than coal plants. They have high source energy factors because of their poor efficiency. Closing them would significantly reduce Vermont’s source energy, and toxic pollution, and CO2 emissions.

 

NOTE: Per government edict, burning trees has been declared CO2-neutral, which is only partially true, plus you have to wait for about 50 to 100 years for just the combustion CO2 to be fully reabsorbed by forest growth, provided the forest, from which the trees were taken, would still be there to do the absorbing and that the forest CO2 absorption/acre is unimpaired by development, clear-cutting, disease, etc. The CO2 of the non-combustion part of the pathway, about 25%, will never be absorbed; most of it just accumulates in the atmosphere, because the world’s CO2 sinks (land and water) are fully used.

http://www.windtaskforce.org/profiles/blogs/is-burning-wood-co-2-ne...

 

Wood Source Energy Factor (district heating plants)

Losses = Upstream (harvest, chipping, transport (2.5%) + Conversion to heat, including site self-use (30%) + Thermal distribution (5%) = 37.5%, i.e., 62.5% arrives at the user heating appliance.

The source energy factor for wood district heating plants is 100/62.5 = 1.6, i.e., the energy equivalent of 0.6 of 1.6 trees is wasted.

 

NOTE: Heating plants are not base-loaded plants. Their conversion efficiency is the seasonal average, which is less than the rated value in brochures.

 

NOTE: District biomass and waste plants can produce electricity and heat. The plant annual average efficiency is dependent on full, year-round utilization of the rejected heat. That efficiency is less than the rated value in brochures.

 

Wood Source Energy Factor	%
Upstream (harvest, chipping, transport)	2.5
Conversion to electricity, including site self-use	30.0
Transmission and distribution	5.0
Total loss	37.5
Arriving at user meters	62.5
Source energy factor 100/62.5	1.6

 

Coal Source Energy Factor

Losses = Upstream (extraction, processing, transporting (4%) + Conversion to electricity, including site self-use (60%) + Transmission and distribution (7%) = 71%, i.e., 29% arrives at the user meters.

The source energy factor for coal power plants is 100/29 = 3.45.

 

In this example a conversion efficiency of 40% was assumed. Ultra-supercritical coal plants have efficiencies up to 45%. Their conversion loss would be 55%.

http://www.windtaskforce.org/profiles/blogs/cop-21-world-renewable-...

 

Coal Source Energy Factor	%
Upstream (extraction, processing, transporting	4.0
Conversion to electricity, including site self-use	60.0
Transmission and distribution	7.0
Total loss	71.0
Arriving at user meters	29.0
Source energy factor 100/29	3.45

 

Gas Source Energy Factor

Losses = Upstream (9%) + Conversion to electricity with CCGT, including site self-use (45%) + T&D (7%) = 61%, i.e., 39% arrives at the user meters.

The source energy factor for gas power plants is 100/39 = 2.56.

 

In this example a conversion efficiency of 55% was assumed. CCGT plants have efficiencies up to 60%. Their conversion loss would be 40%.

 

Gas Source Energy Factor	%
Upstream	9.0
Conversion to electricity with CCGT, including site self-use	45.0
T&D	7.0
Total	61.0
Arriving at user meters	39.0
Source energy factor 100/39	2.56

 

Hydro Source Energy Factor

Losses = Upstream (1%) + Conversion to electricity, including site self-use (5%) + T&D (7%) = 11%, i.e., 87% arrives at user meters.

The source energy factor for hydro power plants is 100/87 = 1.15.

 

The turbines of larger capacity, MW, hydro plants have efficiencies up to 97%.

 

Hydro Source Energy Factor	%
Upstream	1
Conversion to electricity, including site self-use	5
T&D	7
Total	13
Arriving at user meters	87
Source energy factor 100/87	1.15

 

Wind Source Energy Factor

Onshore wind turbine power plants have an energy returned/energy invested, EROEI, of about 18 - 20, for sites with average wind conditions.

http://www.theoildrum.com/node/1863

 

Losses = Upstream (0%) + Site self-use (3%) + T&D (7%) + Peaking, filling in, balancing and storage inefficiency (5%) = 15%, i.e., 85% arrives at user meters.

The source energy factor for wind turbine power plants is 100/85 = 1.18.

 

Wind Source Energy Factor	%
Upstream	0
Conversion to electricity, including site self-use	3
T&D	7
Peaking, filling in, balancing and storage inefficiency	5
Total	15
Arriving at user meters	85
Source energy factor 100/85	1.18

 

PV Solar Source Energy Factor

In a recent study, Bhandari, et al., surveyed 231 articles on photovoltaic technologies, finding that, under average Southern European irradiation, the mean EROEI of the most common PV technology (polycrystalline Si) is about 11 - 12. That EROEI would be less in Vermont, Germany, etc., which have lesser irradiation.

 

http://www.resilience.org/stories/2016-05-24/but-what-s-the-real-en...

http://www.resilience.org/stories/2006-06-16/energy-payback-roof-mo...

 

Losses = Upstream (0%) + Site self-use (1%) + T&D (7%) + Peaking, filling in, balancing and storage inefficiency (5%) = 13, i.e., 87% arrives at user meters.

The PV solar source energy factor is 100/87 = 1.15.

 

PV Solar Source Energy Factor	%
Upstream	0
Site self-use	1
T&D	7
Peaking, filling in, balancing and storage inefficiency	5
Total	13
Arriving at user meters	87
Source Energy Factor 100/87	1.15

 

NOTE: Peaking, filling-in, balancing and storage losses increase as:

 

1) Wind and solar energy becomes a greater percentage of the energy on the grid

2) More transmission build-outs are implemented

3) More storage, including peak shaving storage and seasonal storage is implemented

http://www.windtaskforce.org/profiles/blogs/fuel-and-co2-reductions...

 

APPENDIX 1

Hydro-Quebec A Much Better Alternative Than Wind And Solar: Hydro-Quebec has about 5600 MW of spare hydro plant capacity, the excess water, now spilling over the spillways, could immediately be used to generate electricity. H-Q has under construction and in planning stages an additional 5000 MW of hydro plant capacity. See URL.

Here a list of the benefits of hydro energy:

- Clean (no particulates, no SOX, no NOx)
- Low-cost (5 - 7 c/kWh, plus 1 c/kWh for transmission), much less than wind and solar. See URL.
- Very low CO2/kWh emissions, much lower than wind and solar
- Steady, 24/7/365 energy, i.e., NOT variable and NOT intermittent, unlike wind and solar, which are weather dependent, variable cloudiness dependent, night and day dependent, and season dependent
- NO federal and state subsidies and investment tax credits
- NO capital outlays by Vermont’s government
- NO enriching of multi-millionaires and their lucrative, risk-free, tax shelters
- NO additional environmental impact in Vermont and Canada
- Private entities would own the transmission lines from Quebec to New England
- RECs would not need to be sold to out-of-state entities so they would be wearing the green halo, instead of Vermonters.
- Much less social discord than controversial wind on pristine ridgelines and solar in fertile meadows

 

Here are some URLs about increased hydro energy from Hydro Quebec. Make sure to read them as they contain much valuable information.

 

http://vtdigger.wpengine.com/2015/01/28/utilities-want-flexibility-...

https://finance.yahoo.com/news/eversource-hydro-qu-bec-offer-170400...

http://www.windtaskforce.org/profiles/blogs/increased-canadian-hydr...

http://www.windtaskforce.org/profiles/blogs/more-energy-from-hydro-...

http://www.windtaskforce.org/profiles/blogs/gmp-refusing-to-buy-add...

 

APPENDIX 2

Wind and Solar Increase Fuel Use and CO2 Emissions of Traditional Plants: Variable wind and solar electricity cannot be fed into the grid unless the traditional generators perform the peaking, filling-in and balancing services. This requires: 1) more cold start/stops; 2) more hot, synchronous standby; 3) increased operation at variable outputs; and 4) increased operation at part-load outputs.

 

This reduces their annual production and detracts from their normal, more efficient operation and thus their economic viability; more fuel/kWh, more CO2/kWh, more wear and tear/kWh.

 

That efficiency loss increases with increased wind and solar energy on the grid. It is charged not to owners of wind and solar systems, but to ratepayers. This is another way, in addition to various subsidies, to make that wind and solar appear less costly and “competitive”.

 

For this article, the efficiency loss was assumed at 5%, because wind and solar still are a very small percentage of the total load on the NE grid. In Ireland, with over 20% wind on its grid, the loss is much higher. See URLs.

 

During windy and sunny periods, there often is a surplus of electricity, which lowers wholesale prices.

- Wind and solar usually sell their electricity at fixed prices, likely at above-market feed in tariffs, or under power purchase agreements.

- Traditional plants usually sell their electricity at fixed prices, close to annual average wholesale levels, or at wholesale, an additional adversity when wholesale prices tend towards zero or even become negative.

 

http://www.windtaskforce.org/profiles/blogs/fuel-and-co2-reductions...

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

http://www.windtaskforce.org/profiles/blogs/vermont-speed-renewable...