November 25, 2014
By: Donald Jones, P.Eng., retired nuclear industry engineer, 2014 November 24
Major automobile manufacturers are continuing their development of cars powered by fuel cells using hydrogen (reference 1). Like cars powered by electric batteries the cars themselves will emit no greenhouse gas (GHG). Bulk quantities of hydrogen are mainly derived from natural gas (increasingly frackgas) but the process results in the production of carbon dioxide, a GHG, so fuel cell cars will not reduce overall GHG emissions. However hydrogen can also be produced from the electrolysis of water using electricity. If this electricity is generated from a power grid of non-fossil fuelled generation then zero overall GHG emissions can be achieved – this applies to battery cars as well as fuel cell cars.
Since fuel cell cars and battery cars can significantly reduce GHG emissions in at least part of the transportation sector the market for such vehicles could expand and one of the key questions will be how will these cars affect the demand for electricity and the stability of the grid. Battery cars and fuel cell cars will affect the power grid in different ways. Battery charging is uncontrolled and people will charge their car batteries when convenient, day and night. Fast battery charging at home from a dedicated house circuit can overload the street transformers. Smart controls at the distribution level may alleviate this but ultimately the distribution system might need upgrading to handle the extra demand. All ratepayers will pay for this including those without battery cars. Increasing the day time peak loads on the grid by uncontrolled battery charging will require an increase in generating capacity, likely from frackgas-fired GHG emitting units. Ideally battery charging should be done overnight when surplus generation is available at the lowest carbon dioxide emission intensity and at lowest cost. Read the rest of this entry »
September 25, 2014
By: Donald Jones, P.Eng., retired nuclear industry engineer, 2014 September 24
This comment by Kim Warren, VP of Operations and Chief Operating Officer at The Independent Electricity System Operator (IESO), under the title “Powering Ontario Through Energy Literacy”, appeared in a sponsored feature by Mediaplanet in a “Green Living” supplement to the Toronto Star of 2014 September 24, “There are distinct advantages to having diverse fuels. No system operator likes to see all of their eggs in one basket because every fuel has its advantages and disadvantages, and behaves differently in certain seasonal or weather conditions.” Right, except for nuclear!
Wind obviously depends on the weather. So does solar and both are expensive on a $/kWh basis. Only a small fraction of the installed wind capacity is credited by the IESO to be there when needed at peak times and even then there are no guarantees. Wind can be plentiful when not needed and in short supply when it is needed. Embedded solar tends to fade when needed during the late afternoon peak demand and needs more ramping capacity from generators on the grid. Wind can do the same during the morning peak. People living near the huge wind turbine installations will continue to object to their presence. Despite what the IESO says wind puts a lot more stress on the system operators who have to juggle output from other generators on the grid to compensate for wind’s irregularities. If these are gas-fired units it increases greenhouse gas (GHG) emissions above what might have been expected from the reduction in gas-fired MWh due to the wind generation. Read the rest of this entry »
August 27, 2014
By: Donald Jones, P.Eng., retired nuclear industry engineer – 2014 August
Ontario’s Independent Electricity System Operator (IESO) has a pilot project that uses motor/generator flywheels, batteries, and aggregate loads as short term energy storage to, it says, provide regulation services (reference 1). These short term energy storage systems should not be confused with longer term storage systems like pumped water storage, compressed air, thermal etc. Regulation is secondary frequency control (reference 2) and can be automatic (AGC – automatic generation control) or manual and brings grid frequency back into its narrow control band after an under frequency or over frequency event has been arrested and the grid stabilized by fast acting primary frequency control/response. This regulation service is normally supplied by selected hydroelectric units at Niagara Falls and even by Ontario’s coal fired units before they were shutdown. Combined cycle gas turbine (CCGT) units can also be used to provide regulation service.
The addition of large amounts of unreliable wind generated electricity to the Ontario grid will/has caused a deterioration in frequency control (reference 3). Wind does not provide any passive inertial response/energy storage capability or active primary frequency control. The wind generation displaces conventional generation on the grid, initially the CCGTs and then some hydroelectric, with the consequent loss of the passive inertial response (energy storage capability) of the rotating masses of the conventional units to help limit frequency perturbations from such things as wind gusts on the wind generators. As well this results in the loss of the active primary frequency control capability of the conventional units. Primary frequency control is automatic and is provided by the speed governors of individual generating units to very rapidly arrest any drift in frequency due to mismatches in supply and demand on the grid. Primary frequency control is essential for grid stability. Reduced amounts of primary frequency response on the system can result in under-frequency load shedding and cascading outages. Since the nuclear units are presently operated in their turbine-following-reactor mode of operation they cannot provide primary frequency control and only provide passive inertial response (reference 2). This means that during periods of surplus baseload generation (SBG) that usually occur when demand is low and wind conditions are favourable all the large CCGT units and some hydro units are shutdown so frequency response on the Ontario grid will solely depend on the primary frequency response of the operating hydroelectric units with enabled speed governors and the energy storage (inertial response) capability of the nuclear and hydroelectric units. This results in a jittery grid caused by wind gusts and larger swings in frequency after an upset resulting in the need for more megawatts of secondary frequency control/regulation to return grid frequency back into its narrow control band. During periods of SBG without wind generation the grid would still not have the inertial response of most of the gas-fired generators but would be more stable because it would not be subject to the rapid frequency upsets from wind. The shutdown of the CCGTs and some hydro because of SBG, with or without wind generation, also means that the reactive power support and voltage control provided by these units is no longer available with, apparently, little if any affect on grid voltage? If voltage support were a concern and the CCGTs and hydro units did not have a synchronous condenser mode of operation, which they likely don’t, then other equipment that provide local voltage support would have to be used. Read the rest of this entry »