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Our society has become highly dependent on reliable grid supplied electricity.
Electricity is electromagnetic field energy that is generated, guided by transmission lines over long distances and then used to do work. Grid supplied electricity is widely used to provide power on demand when and where needed.
Grid supplied electricty is used to power socially critical applications such as fresh water pumping, sewage pumping, lighting, communications, signalling and electric transit. Grid supplied electricity is also routinely used to control other energy sources.
It can be shown that at any point along two parallel guiding conductors that have identical currents flowing in opposite directions the instantaneous energy flux is equal to the product:
(instantaneous current through the conductors) X (instantaneous voltage between the conductors)
The energy propagation velocity along a transmission line is dependent on the exact materials, geometry and frequency but is usually close to the speed of light.
The end to end (generator shaft to motor shaft) efficiency of a low frequency (~ 60 Hz) electricity system is typically in the range 60% to 90%. An issue that is not adequately appreciated is the role of reflected power in AC power systems. If reflected power is present the electrical energy delivery capacity of a transmission system can be severely reduced.
Measurements of delivered electrical energy indicate the capacity of the delivered electrical energy to do work.
During the 20th century most electricity generation in Ontario was done at large central plants. Electricity was transmitted to customers via high voltage AC transmission lines that fed local distribution networks.
After Ontario Hydro developed the large easily accessible hydro-electric resources in southern Ontario, it built large coal and nuclear thermal generation plants that relied on direct lake water cooling.
For safety and environmental protection reasons it is anticipated that future nuclear generation plants will rely on use of dry cooling towers for heat dissipation. The problems at Fukushima Daiichi demonstrated the inherent dangers of building nuclear power stations at close to the level of a large body of water. Earthquakes and related tsunamis are rare, but when they do occur they can cause extensive damage.
Nuclear electricity generating stations are more expensive than the coal electricity generating stations but the coal fired plants emit carbon dioxide and toxic products of combustion.
Excess carbon dioxide in the atmosphere and in the oceans has become a threat to the continued existence of mankind. The toxic products of combustion of coal are also a major public health problem. The soot resulting from combustion of fossil hydrocarbons contributes to melting of both glaciers and floating ice.
IPCC CO2 emission data from electricity systems around the world shows that the lowest emission large electricity systems (< 40 gms CO2 / kWh) contain a high penetration of hydroelectric and/or nuclear generation. Electricity systems with a high penetration of variable renewable generation (wind and solar) have much higher average CO2 emissions (~ 228 gms CO2 / kWhe for natural gas backup to ~ 557 gm CO2 / kWhe for coal backup). Purely coal based electricity generation emits about 973 g / kWhe.
The reason for the higher average CO2 emissions from electricity systems containing variable renewables is that in most jurisdictions zero emission storage technologies are too expensive and inefficient to provide the backup electricity generation required at times when the variable renewable generation cannot meet the electricity load. The energy source for the backup electricity generation used with variable renewable generation is usually a fossil fuel. The result is much higher average CO2 emission levels in electricity systems with variable renewable generation than in electricity systems that rely heavily on hydroelectric and/or nuclear generation. Exceptional situations exist in British Columbia, Quebec and Norway where due to local geography much of the electricity comes from hydroelectric power and where mountain valleys have permitted construction of large amounts of seasonal hydraulic energy storage.
The recent average CO2 emission levels of a few large electricity systems are tabulated below.
|YEAR||CO2 EMISSION |
(g / kWhe)
|PJM||2016||450||fig. 3 http://www.pjm.com/~/media/library/reports-notices/special-reports/20170317-2016-emissions-report.ashx|
To achieve rapid and deep (>80%) carbon dioxide emission reductions, the most cost effective solution using currently available technologies is to increase the penetration of hydroelectric and/or nuclear generation, especially for base load (24 hour a day) energy requirements. That is just one of many inconvenient engineering facts about climate change mitigation that many people are reluctant to accept.
Ontario has now taken its coal fired electricity generation plants out of service, has replaced them with a mix of natural gas combined cycle gas turbines (CCGT) and simple cycle gas turbines (SCGT) and is building further electricity generation using non-fossil fuel technologies. Ontario needs to develop sufficient new non-fossil electricity generation capacity to both replace existing natural gas fired electricity generation and to displace fossil fuels in the transportation and heating sectors.
DISTRIBUTED RENEWABLE GENERATION:
As compared to wind generation nuclear thermal generation has the disadvantage that about two units of heat must be dissipated at the reactor site for every unit of electrical energy generated. Provided that the thermal electricity generation facility can efficiently track the instantaneous electricity load this heat dissipation can be mitigated but not prevented through use of distributed renewable energy generation. Thus in future nuclear power plants thermally efficient load tracking may be an important performance feature. In practise high thermal efficiency is best achieved using multiple step controlled steam turbines, so that each steam turbine operates at a high energy conversion efficiency. This control methodology requires automatic pre-synchronization of the next steam turbine to be loaded.
POWER MATCHING CONSTRAINT:
Electricity systems operate under the constraint that total instantaneous power generation must always equal total instantaneous load power. If some portion of the total generation is intermittent then complaince with this power matching constraint requires energy storage and/or load control.
Distributed energy storage must be added behind both generator and load electricity meters to level outputs from wind generators and to improve the utilization of the generation, transmission and distribution systems. Large reservoir dammed hydraulic energy storage, dispatchable synthetic liquid fuel production and dispatchable electro-chemical processing are required to provide efficient daily and seasonal balancing of intermittant renewable electricity generation.
An electricity rate with a low marginal cost per kWh when there is surplus non-fossil power is needed to financially enable energy storage and cost effective fossil fuel displacement. The electricity rate at other times should be primarily based on the registered peak kW demand or peak kVA damand during each billing period.
ELECTRICITY SYSTEM EVOLUTION:
A balanced one hour presentation relating to the optimal electricity system evolution in North America is: Jesse Jenkins April 2019 Video.
In order to completely displace fossil fuels and hence limit global warming, the per capita installed non-fossil electricity generation and corresponding transmission capacity must be increased several fold. Of particular near term importance is prevention of real estate development along corridors that in the future will be required for energy transmission or in river valleys that in the future will be required for hydraulic energy storage.
The electricity generation, storage, transmission and distribution infrastructure must be sufficient to allow rapid population growth in Ontario to accommodate people who are forced to migrate to Ontario from other countries due to rising sea levels, drought and conflict resulting from CO2 triggered climate change.
The change from an electricity transmission and distribution network based on central generation to an electricity system containing significant distributed electricity generation requires changes to the metering methodology, electricity rates, voltage regulation methodology, fault isolation switchgear and system control. The output variability of wind, solar and hydraulic generators requires additional investment in electricity transmission and energy storage.
The present use of dispatched natural gas fired combustion turbine generation for load following must be replaced by dispatch of load used for: displacing fossil fuels, charging energy storage and production of synthetic liquid fuels.
FUTURE RATE STRUCTURE:
The generator compensation rate structure should contain strong financial incentives to encourage every distributed generator to maximize capacity factor and to contribute to grid voltage stabilization.
To enable behind the meter energy storage and to minimize transmission/distribution costs electricity rates applicable to both generators and loads must financially reward parties that normally input or output electricity at a nearly constant rate.
In order to financially enable energy storage there must be public certainty that for at least a decade into the future the marginal on-peak electricity rate per kWh will be at least three times the marginal off-peak electricity rate per kWh. Absent that minimum daily rate swing behind the meter energy storage is not economical for its owner and hence will not be built. Absent energy storage intermittant renewable electricity generation is not economic due to its unreliability and inefficient use of transmission / distribution resources.
In order to financially enable construction of required transmission/distribution, transmission connected generators should pay for transmission costs at the same rate as LDCs and distribution connected generation should pay for distribution at the same rate as retail load customers. Otherwise electricity rates are distorted and the required transmission/distribution is not built when and where required. Unless generators directly pay for the transmission/distribution that they use the generators lack sufficient influence over transmission/distribution planning and lack financial incentive to operate at a high capacity factor.
LACK OF POLITICAL WILL:
Ontario politicians have repeatedly demonstrated lack of political will to impose a fossil carbon tax. The availability of low cost natural gas fuelled electricity generation presently prevents the wide daily swings in electricity price that are required to financially enable behind the meter energy storage. Absent energy storage most renewable electricity generation does not make economic sense because it does not reliably meet the instantaneous power requirements of the firm load. This politically absurd situation makes Ontario overly dependent on nuclear power.
The electricity system needs a combination of fast neutron reactors and interruptible loads to enable non-fossil generation tracking of uncontrolled load. The lead time for fast neutron reactor development and deployment is likely close to 20 years. The lead time for large scale deployment of interruptible load is comparable. The politicians have totally failed to face this energy system planning reality.
This web page last updated April 23, 2019.
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