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PHEVs have within them the energy source and power electronics capable of producing electricity that can be converted to 50-60Hz AC which is same as the one power homes and offices. When electricity flows from cars to power lines, it is called "vehicle to grid" power, or V2G. Cars pack a lot of power: one typical electric-drive vehicle can produce 10kW, the average draw of 10 houses.

When considered only for daily peak or base-load power, the economics may not be favorable to battery storage because the resulting battery wear-out costs per kWh are too high.

There are two areas in which the economic viability needs to be explored.
-First, other energy services, including hour-ahead, spinning reserves, and others can have high values, above their cost in battery wear-out.
-Second, batteries for electric vehicles have two general types of wear out.

These are degradation due to use (cycling) and degradation due to calendar time. There is some evidence that suggests that calendar life may prove to be the life limiting factor for some EV batteries and not necessarily the cycling time. If this is the case, the incremental cost of additional cycling within the calendar life may be small or even zero.

Some of the value-generating services that could be offered by electric and hybrid vehicles don't require significant energy transfer. For example, peak power sold as spinning reserves to the ISO or dispatchable power to the distribution company may be activated only a few times per year. Reactive power or grid support services would not require any net energy flow from the vehicle.

4.2 V2G and Power markets

Electricity is grouped in several different markets with correspondingly different control regimes. Here we discuss four of them—baseload power, peak power, spinning reserves, and regulation—which differ in control method, response time, duration of the power dispatch, contract terms, and price. We focus particularly on spinning reserves and regulation, which must deliver power within minutes or seconds of a request.

All these electricity resources are controlled in real-time by either an integrated electric utility or an Independent System Operator.

Baseload power

Baseload power is provided round-the-clock. In India this typically comes from coal-fired plants that have low costs per kWh. Baseload power is typically sold via long term contracts for steady production at a relatively low per kW price. V2G has been studied across multiple markets of US which have a similar structure, showing that EVs cannot provide baseload power at a competitive price. This is because baseload power hits the weaknesses of EVs—limited energy storage, short device lifetimes, and high energy costs per kWh—while not exploiting their strengths—quick response time, low standby costs, and low capital cost per kW.

Peak power is generated or purchased at times of day when high levels of power consumption are expected—for example, on hot summer afternoons. Peak power is typically generated by power plants that can be switched on for shorter periods, such as gas turbines. Since peak power is typically needed only a few hundred hours per year, it is economically sensible to draw on generators that are low in capital cost, even if each kWh generated is more expensive. Our studies have shown that V2G peak power may be economic under some circumstances. The required duration of peaking units can be 3–5 h, which for V2G is possible but difficult due to on-board storage limitations. Vehicles could overcome this energy-storage limit if power was drawn sequentially from a series of vehicles.

Spinning reserves refers to additional generating capacity that can provide power quickly, say within 10 min, upon request from the grid operator. Generators providing spinning reserves run at low or partial speed and thus are already synchronized to the grid. Spinning reserves are the fastest response, and thus most valuable, type of operating reserves; operating reserves are “extra generation available to serve load in case there is an unplanned event such as loss of generation.”

The provision of spinning reserves is practically absent in India currently due to the high cost of implementation, the perpetual deficit, the high fuel costs and also lack of sufficient evacuation infrastructure. Spinning reserves globally are paid for by the amount of time they are available and ready. For example, a 1MWgenerator kept “spinning” and ready during a 24-h period would be sold as 1MW-day, even though no energy was actually produced. If the spinning reserve is called, the generator is paid an additional amount for the energy that is actually delivered (e.g., based on the market-clearing price of electricity at that time).

The capacity of power available for 1 h has the unit MW-h (meaning 1MW of capacity is available for 1 h) and should not be confused with MWh, an energy unit that means 1MW is flowing for 1 h. These contract arrangements are favorable for EVs, since they are paid as “spinning” for many hours, just for being plugged in, while they incur relatively short periods of generating power. Contracts for spinning reserves limit the number and duration of calls, with 20 calls per year and 1 h per call typical maxima. As spinning reserves dispatch time lengthens, from the typical call of 10 min to the longest contract requirement, 2 h, fueled vehicles (PHEVs) gain advantage over battery vehicles because they generally have more energy storage capacity and/or can be refueled quickly for driving if occasionally depleted by V2G.

Spinning reserves, along with regulation are forms of electric power referred to as “ancillary services” or A/S. Ancillary services account for 5–10% of electricity cost, or about $ 12 billion per year in the U.S., with 80% of that cost going to regulation.

Regulation

Regulation, also referred to as automatic generation control (AGC) or frequency control, is used to fine-tune the frequency and voltage of the grid by matching generation to load demand. Regulation must be under direct real-time control of the grid operator, with the generating unit capable of receiving signals from the grid operator’s computer and responding within a minute or less by increasing or decreasing the output of the generator. Depending on the electricity market and grid operator, regulation may overlap or be supplemented by slower adjustments, including “balancing service” (intra hour and hourly) and/or “load following.”

Some markets split regulation into two elements: one for the ability to increase power generation from a baseline level, and the other to decrease from a baseline. These are commonly referred to as “regulation up” and “regulation down”, respectively. For example, if load exceeds generation, voltage and frequency drop, indicating that “regulation up” is needed. A generator can contract to provide either regulation up, or regulation down, or both over the same contract period, since the two will never be requested at the same time.

Markets vary in allowed combinations of up and down, for example, PJM Interconnect requires contracts for an equal amount of regulation up and down together, whereas California Independent System Operator (CAISO) is more typical in allowing contracts for just one, or for asymmetrical amounts (e.g., 1MW up and 2MW down).

Regulation is controlled automatically, by a direct connection from the grid operator (thus the synonym “automatic generation control”). Compared to spinning reserves, it is called far more often (say 400 times per day), requires faster response (less than a minute), and is required to continue running for shorter durations (typically a few minutes at a time).

The actual energy dispatched for regulation is some fraction of the total power available and contracted for. We shall show that this ratio is important to the economics of V2G, so we define the “dispatch to contract” ratio as

where Rd–c is the dispatch to contract ratio (dimensionless), Edisp the total energy dispatched over the contract period(MWh), Pcontr the contracted capacity (MW), and tcontr is the duration of the contract. Rd–c is calculated separately for regulation up or down.

Three independent factors limit V2G power:

(1) The current-carrying capacity of the wires and other circuitry connecting the vehicle through the building to the grid

(2) The stored energy in the vehicle, divided by the time it is used

(3) The rated maximum power of the vehicle’s power electronics.

The lowest of these three limits is the maximum power capability of the V2G configuration. We develop here analysis for factors 1 and 2, since they are generally much lower than 3.

Vehicle-internal circuits for full-function electric vehicles are typically upwards of 100kW. For comparison, average home maximum power capacity is typically 20–50kW, with an average draw closer to 1-2 kW in urban environments. To calculate the building-wiring maximum, one needs only the voltage and rated ampere capacity of the line:

where Pline is power limit imposed by the line in watts (here usually expressed in kW), V the line voltage, and A is the maximum rated current in amperes. For example, home wiring at 240V AC, and a typical 50A circuit rating for a large-current appliance such as an electric range, the power at the appliance is 50A×240V so it yields a line capacity of 12kW maximum for this circuit. Based on typical home circuits, some would be limited to 10kW, others to 15kW as the Pline limit. For a commercial building, or a residential building after a home electrical service upgrade (at additional capital cost), the limit could be 25kW or higher.

On the vehicle side, most existing (pre-V2G) battery vehicle chargers use the National Electrical Code (NEC) “Level 2” standard of 6.6kW. The first automotive power electronics unit designed for V2G and in production, by AC Propulsion, provides 80A in either direction, thus, 19.2kW at a residence (240 V). This V2G unit has been used in one prototype plugin hybrid and several battery electric vehicles for various studies in US.

Power limited by vehicle’s stored energy

The previous section analyzed V2G power as limited by the line capacity. The other limit on V2G power is the energy stored on-board divided by the time it is drawn. More specifically, this limit is the onboard energy storage less energy used and needed for planned travel, times the efficiency of converting stored energy to grid power, all divided by the duration of time the energy is dispatched. This is calculated as

where Pvehicle is maximum power from V2G in kW, Es the stored energy available as DC kWh to the inverter, dd the distance driven in miles since the energy storage was full, drb the distance in miles of the range buffer required by the driver, ηveh the vehicle driving efficiency in miles/kWh, ηinv the electrical conversion efficiency of the DC to AC inverter (dimensionless), and tdisp is time the vehicle’s stored energy is dispatched in hours.

In a specific application, dd would depend on the driving pattern, the vehicle type (e.g., battery EVs may be recharged at work), and the driver’s strategies for being prepared to sell power.

The fuel cell vehicle, or hybrid in motor-generator mode, can provide only regulation up (power flows from vehicle to grid), not regulation down (power from grid to vehicle), so it has no analogy to the battery EV’s recharge during regulation down. Power capacity of V2G is determined by the lower of the two limits, Pline or Pvehicle.

The economic value of V2G is the revenue minus the cost.

The formulas for calculating revenue depend on the market that the V2G power is sold into. For markets that pay only for energy, such as peak power and baseload power, revenue is simply the product of price and energy dispatched. This can also be expanded, since energy is P* t,

where r is the total revenue in any national currency, pel the market rate of electricity in Rs/kWh, Pdisp the power dispatched in kW (for peak power Pdisp is equal to P, the power available for V2G), and tdisp is the total time the power is dispatched in hours.

On an annual basis, peak power revenue is computed by summing up the revenue for only those hours that the market rate (pel) is higher than the cost of energy from V2G.

For spinning reserves and regulation services the revenue derives from two sources: a “capacity payment” and an “energy payment.” The capacity payment is for the maximum capacity contracted for the time duration (regardless of whether used or not). For V2G, capacity is paid only if vehicles are parked and available (e.g., plugged-in, enough fuel or charge, and contract for this hour has been confirmed). The energy payment is for the actual kWh produced; this term is equivalent to what the equation helps calculate as revenue from either spinning reserves or regulation services, with the first term being the capacity payment and the second term the energy payment.

where pcap is the capacity price in Rs/kW-h, pel is the electricity price in $/kWh, P is the contracted capacity available (the lower of Pvehicle and Pline), tplug is the time in hours the EV is plugged in and available, and Edisp is the energy dispatched in kWh.

where Ndisp is the number of dispatches, Pdisp the power of each (presumably equal to the vehicle capacity P), and tdisp is the duration of each dispatch in hours. A typical spinning reserves contract sets a maximum of 20 dispatches per year and a typical dispatch is 10 min long, so the total Edisp will be rather small.

Thus, for forecasting regulation services revenue we substitute the outcome from the above equation in the earlier equations to get.

The cost of V2G is computed from purchased energy, wear, and capital cost. The energy and wear for V2G are those incurred above energy and wear for the primary function of the vehicle, transportation. Similarly, the capital cost is that of additional equipment needed for V2G but not for driving. Assuming an annual basis, the general formula for cost is

where c is the total cost per year, cen the cost per energy unit produced (calculated below), Edisp the electric energy dispatched in the year, and cac is the annualized capital cost.

For regulation, substituting values of Edisp computed by

Thus the total annual cost to provide regulation is

where cen is the per kWh cost to produce electricity. The equation for cen includes a purchased energy term and an equipment degradation term

where cpe is the purchased energy cost, and cd is the cost of equipment degradation (wear) due to the extra use for V2G, in Rs/kWh of delivered electricity. The purchased energy cost cpe is the cost of electricity, hydrogen, natural gas, or gasoline, expressed in the native fuel cost units (e.g., Rs/kg Natural Gas), and ηconv is the efficiency of the vehicle’s conversion of fuel to electricity (or conversion of electricity through storage back to electricity). The units of ηconv are units of electricity per unit of purchased fuel. Thus equations computed cen, the cost of delivering a unit of electricity, is expressed in Rs/kWh regardless of the vehicle’s fuel.

Degradation cost, cd, is calculated as wear for V2G due to extra running time on a hybrid engine or fuel cell, or extra cycling of a battery. Shallow cycling has less impact on battery lifetime than the more commonly reported deep cycling.

As the vehicle fleet moves to electric drive (hybrid, battery, and fuel cell vehicles), an opportunity opens for “vehicle-to-grid” (V2G) power. V2G only makes sense if the vehicle and power market are matched. For example, V2G appears to be unsuitable for baseload power—the constant round-the clock electricity supply—because baseload power can be provided more cheaply by large generators, as it is today. Rather, V2G’s greatest near-term promise is for quick-response, high-value electric services. These quick-response electric services are purchased to balance constant fluctuations in load and to adapt to unexpected equipment failures.

The results suggest that the engineering rationale and economic motivation for V2G power are compelling. The societal advantages of developing V2G include an additional revenue stream for cleaner vehicles, increased stability and reliability of the electric grid, lower electric system costs, and eventually, inexpensive storage and backup for renewable electricity.

Chapter 5

Findings and Conclusion

The power sector in India is a fast maturing one and ancillary services are currently provided mandatorily by different sections of the industry like the generating companies. But it has been observed that the ancillary services are of great importance and need to be taken separately. As per the Indian Electricity Act of 2003, competition is to be promoted in every sphere of the sector and the proposed staff paper by CERC on Ancillary Services Market aims to do the same. The three types of ancillary services that are slated to be opened to market operation are – Frequency Control Ancillary Service, Network Control Ancillary Service and System Restart Ancillary Services.

It has been studied that grid connected electric vehicles are capable of providing aforementioned ancillary services. The electric vehicles industry is fast growing with rising adoption in the developed country markets. Not only do they provide a relatively cheaper cost of operation, they also offer other benefits like reduced emissions in cities and also reduce the dependency of oil. It was found that the biggest barrier to large scale adoption of electric vehicles was two-fold.

The first was a very high upfront cost. Electric vehicles cost considerably more than their conventionally powered counter parts. The second is the lack of charging infrastructure in public places which limits the electric range of the vehicles. To tackle the first problem, the governments of the world are providing heavy subsidies and incentives. Countries like Norway provide incentives that can amount up to $8200 per car per year. For the second hurdle, an increasingly large charging base is being developed in public places in the developed nations. Also plug-in hybrid electric vehicles have successfully extended the range of the vehicles by using petrol or natural gas as a secondary fuel thereby reducing the psychological fear of range limitation people had in their mind linked to electric vehicles.

It has been shown in various researches across the world that vehicle to grid operations are a feasible possibility as modern electric vehicles can be equipped with bidirectional inverters that can not only use energy from grid to charge themselves but also supply energy back to the grid if demanded. This has been made possible with the use of smart grids that can communicate with such distributed storage infrastructure.

In a country like India where normal generating stations face multiple challenges such as fuel supply and environmental clearances, Electric Vehicles can become a suitable alternative in providing short term power in the form of ancillary services. The Government of India introduced the National Electric Mobility Mission in 2012 that aims to facilitate the adoption of electric vehicles by providing incentives and subsidies at both the customer end and the manufacturers end.

This opportunity can be utilized to create infrastructure in the form of large parking stations which provide grid connectivity in the form of charging connections to the electric vehicles. it can provide a win-win situation for all players where the vehicle owners and the parking station can offer their vehicles and infrastructure to provide ancillary services to the grid, the system operators and power sector benefits from the increased grid reliability and the reduced dependence on oil because of the use of electric vehicles also helps reduce pollution in cities and curb the large outflow of foreign exchange in the form of payments for oil imports.

As the Indian markets are still developing and highly price sensitive, the use of this technology can be promoted by first adoption by government bodies themselves in the form of public transport fleets. That has advantages in itself as the parking infrastructure and the parking and driving durations are much more certain in that case rather than that of private vehicles. Also it has been learnt from the example of adoption of CNG vehicles in Delhi that once the technology is demonstrated to be functional, economical and successful by use in public transport, the mass adoption increases manifold.

It will be ideal if government agencies took the lead and switched their bus fleets from convention gas or diesel powered vehicles to smart, grid connected electric vehicles and also increase the pace of implementation of smart grids. Thereby not only unleashing the technical and financial potential of using electric vehicles to provide ancillary services but also offering the citizens cleaner air in cities and reducing the burden on the nation’s forex reserves.

Future Study

Electric vehicles can also be used to mitigate the variability issues with renewable energy sources such as wind and solar. These renewable sources of energy cannot be perfectly estimated or predicted thereby creating variability issues. A recent order on accurate scheduling for renewable energy sources also ran into difficulties due to the inability to perfectly schedule the production through such renewable sources.

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