by Laura Burkhardt and Roger Gray
New York’s electric grid is often referred to as “a tale of two grids”: the upstate section where large generating stations produce more electricity than is consumed and the downstate section where more electricity is consumed than is generated. But there is a “third grid” in the form of small-scale solar on built environments that can help to balance supply vs. load, especially in the Hudson Valley and other downstate regions. This third grid is essential to meeting our goals for a grid powered by 100% renewable energy.
This load vs. supply imbalance is currently addressed by high voltage transmission lines which send unneeded power from upstate to downstate regions where it can be utilized. But during periods of high demand, constraints along key transmission lines can limit the amount of energy otherwise delivered downstate. The result is that not all renewable sources in the system today are being used to their full advantage. When demand is low, wind generation is high, and the transmission system is constrained, NYISO grid operators must curtail output from area wind farms in order to maintain grid reliability; wind farm operators must then reduce their output. This situation occurred in May, June, and October 2018, for example, among other instances. [2]
The state has been working since 2014 to correct this situation with a historic level of investment in the transmission system. In July 2022 Gov. Kathy Hochul announced the commissioning of the Empire State Line, a project that upgrades the energy transmission system that serves Western New York with a new, 20-mile 345 kilovolt line. Other new transmission projects approved or currently under consideration include the AC Transmission Project and The Long Island Offshore Wind Export Public Policy Transmission Need. [3]
In order to achieve the 100% renewable energy grid mandated in New York’s Climate Leadership and Community Protection Act (CLCPA), the state is currently focusing on building large-scale solar and wind projects in upstate areas. The completed and planned transmission improvements will help to get this energy downstate. But we still need small scale solar!
Why We Need Small-Scale Solar on Built Environments
Large-scale ground-mount solar farms and transmission upgrades are essential for meeting our renewable energy goals. From an economic perspective, centralized utility-scale renewables are much cheaper than distributed resources (e.g., solar canopies in parking lots, rooftop panels) due to economies of scale. As of November 2018, the levelized cost (the net present value of the cost of electricity generation over a plant’s lifetime) of rooftop solar was estimated [3a] to be anywhere from 4.5 to 7 times more expensive per MWh relative to utility-scale solar.
In addition to being cheaper, centralized projects are often much easier for the grid operator to control. Because distributed renewables are often small and behind the meter, they can be very difficult to track from a grid operator’s perspective and can significantly complicate load forecasting. [3b]
But small-scale solar installations on built environments are also very important. Here’s why.
Locally generated energy can power emergency shelters and microgrids. Solar-powered emergency shelters can provide power for essential services such as phone charging, EV charging, emergency housing and meals when the grid is down, whether due to severe weather or other conditions. In 2018, for example, SUNY New Paltz completed installation of six separate solar PV arrays (five roof-mounted and two ground-mounted systems) totaling 278 KW, along with a battery storage unit. [4,5] The battery storage unit will be used at times of high electric demand and during emergencies or power outages to support the college’s designated emergency shelter for the campus and community at the college’s Elting Gymnasium.
A microgrid is a resiliency zone – it is essentially a smaller grid that can operate independently, disconnecting from the larger grid during outages. In 2021 Green Mountain Power (GMP) broke ground on a cutting-edge utility microgrid in Panton, Vermont, which will use an existing 4.9-megawatt solar facility with utility-scale batteries already up and running in the town. [6,7] This project is unique because GMP is believed to be the first utility in the country to island a distribution circuit using inverter-based sources with no reliance on fossil fuel generation backup.
In the event of storm damage or a prolonged grid outage, the Panton microgrid will enable backup power from the batteries and solar panels to flow to a network of customers served by the traditional grid. The concept is called “islanding,” and it creates backup power that can work independently from the larger electric system when needed. In Panton, the tracker solar panels follow the sun and can stretch the battery backup power for days, if necessary. This will keep the power on during outages for about 50 customers in Panton to start, with the planned possible expansion of the coverage area to include another 900 customers on that circuit. The batteries are also used to lower costs for all GMP customers during peak energy times.
Locally generated electricity reduces the power loss that occurs over long transmission distances. Electricity has to be transmitted from large power plants to the consumers via extensive networks. Transmission over long distances, which occurs in New York via alternating current (AC) cables, creates power losses. The major part of the energy losses occur as heat lost in the conductors.
AC systems also suffer energy loss through induction (electromagnetic fields). The power through an AC cable is comprised of active and reactive power. Active power is what is what is used for the end purpose, e.g., to provide heat or turn the lights on. Reactive power enables the electromagnetic fields that are needed to transmit energy. The longer the cable, the more reactive power it needs, until at a certain distance only a small fraction of the cable capacity is used for the active power. This is especially a problem for offshore wind farms. [10]
For the years 2017 - 2021 the percent of energy lost over transmission and distribution (T&D) lines in New York State is shown in Table 2. To calculate T&D losses as a percentage, the figure for estimated losses is divided by the result of total disposition minus direct use. Direct use electricity is the electricity which is generated mainly at non-utility facilities and is not put onto the electricity transmission and distribution grid; therefore direct use electricity does not contribute to T&D losses. [10a]
Table 2. Energy Lost over Transmission and Distribution Lines in New York State
Data from New York Energy Profile – U.S. Energy Information Administration [10b]
Some communities object to large-scale solar farms. These objections take various forms. Neighbors of a proposed solar site may claim that the project will reduce their property values or degrade the scenic landscape. A site may be a Native American sacred site or burial site. Or a county may want to preserve its farmland for agricultural use.
But a study by Dr. Richard Perez, a researcher at University of Albany, found that New York contains several hundred square miles of built environments that could be reasonably used for solar installations. [11] This study looked at the area occupied by different types of built environments and made an estimate of how much of that area could potentially host solar panels. The results were as follows:
Roof utilization = 185 sq. miles
Power lines rights of way utilization = 161 sq. miles
Gas pipeline rights of way = 21 sq. miles
Railroads rights of way = 21 sq. miles
Expressways rights of way (center lanes) = 12 sq miles
Landfills/industrial/mining exclusion zones surface utilization = 29 sq. miles
Parking lots utilization = 24 square miles
In addition, a 2019 study by NREL [11a], showed that there are also 210 sq. miles [11c] of human-made water bodies in New York state that are suitable for development of floating photovoltaic (FPV) systems. The study was limited to human-made bodies of water because human-made reservoirs are more likely to be managed and therefore have infrastructure and roads in place. This can ease the FPV installation process. In addition, FPV installations on managed bodies of water may have fewer environmental concerns than installations on natural water bodies; they can also reduce evaporation and algae growth, lower PV operating temperatures, and potentially reduce the costs of solar energy generation. [11b]
A demonstration FPV project is underway in Cohoes, New York [11d]. This 3.2 MW project is sited on the city’s 10-acre reservoir, which was deemed the best approach for a municipality lacking suitable land or rooftops for solar, and it will power all Cohoes city-owned buildings and streetlights.
To summarize, there is an adequate area of built environments (ground surface, rooftop, water) for deploying solar installations.
Small-scale solar can avoid some of the environmental downsides of utility-scale solar farms. For example, installing solar on built environments involves minimal tree cutting while preserving the original purpose of the site. All plants, but especially trees, are very important as carbon sinks. So the more we can avoid cutting trees, the better. Some sources cite 48 pounds per year as the amount of carbon dioxide that a mature tree can absorb. [12] But the operative word here is “mature”. To take a longer-term perspective, if we plant one silver maple today, in 25 years—assuming it survives—it will have sequestered about 400 pounds of carbon dioxide, according to the U.S. Energy Information Administration. But the average U.S. resident emits the equivalent of around 20 tons of CO2 a year [13], so we still need a lot of trees.
In many cases, built environments (e.g., roofs, parking lots, landfills/industrial/mining exclusion zones) do not have trees that need to be cut. And generally speaking the site will maintain its original purpose. Additional benefits occur in the case of parking lots, where solar canopies provide shade for the cars parked underneath, thereby saving fuel (less A/C needed to cool the cars) and preventing loss of capacity in EV batteries.
Another environmental downside is the heat island created by installing a solar farm on green space. The term “heat island” describes built up areas that are hotter than nearby rural areas. The “urban heat island” (UHI) effect describes the phenomena where temperatures in densely populated cities can be significantly higher than in surrounding areas because structures such as buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies. [13a,13b] .
But there is also a “photovoltaic heat island” (PVHI) effect produced by utility-scale solar installations on large tracts of green land such as farms. Studies [13c] indicate that solar installations cause a PVHI effect that warms surrounding areas, thereby potentially influencing wildlife habitat, ecosystem function in wildlands, and human health and even home values in residential areas.
Curtailed wind that is generated upstate could be used to produce green hydrogen for fuel cells instead of being transmitted downstate. If downstate New York could supply more of the electricity that it uses, less wind-generated electricity would need to be transmitted from upstate. This excess wind could then be used to generate green hydrogen by electrolysis.
Hydrogen will be an important component in decarbonizing our economy. It should not be used as a fuel to generate electricity but could be used in fuel cells to power sectors that cannot be easily converted to use electricity such as marine shipping, heavy-duty trucking, high-temperature industrial process heating, ironmaking, and aviation. Another use would be to replace conventional batteries in equipment and vehicles currently powered by electricity with hydrogen fuel cell systems.
Hydrogen would also be necessary for powering backup generators. Generators using hydrogen fuel cells rather than gasoline or diesel are currently manufactured by companies such as GenSure and Altergy. These generators would be necessary for institutions such as hospitals that must have backup power in situations when the grid goes down. It is essential that these hydrogen fuel cells be produced using green hydrogen – hydrogen generated by the steam methane reforming process would defeat the goal of reducing emissions. An adequate supply of green hydrogen fuel cells must be available to operate such generators.
Solar installations on built environments would free up open space that could be used for carbon sequestration. One of the key findings presented in the CLCPA is the importance of large-scale carbon sequestration and strategic land use planning. The CLCPA states:
Large-scale carbon sequestration opportunities include lands and forests and negative emissions technologies. Protecting and growing New York’s forests is required for carbon neutrality. Negative emissions technologies (such as the direct air capture of CO2) may be required if the state cannot exceed 85% direct GHG emissions reductions by 2050. Strategic land use planning will be essential to balance natural carbon sequestration, agriculture activities, new renewables development, and smart urban planning (smart growth).
By locating solar panels on parking lot canopies and rooftops, open space would be preserved for carbon sequestration, thus supporting an important goal of CLCPA.
Small-scale solar installations can become part of a Virtual Power Plant. A Virtual Power Plant (VPP) is a network of decentralized, medium-scale power generating units that are monitored, coordinated and controlled by a central control system. Typically these generating units are renewable energy resources such as rooftop solar, solar carports and other small solar installations, wind farms and battery storage. By being aggregated in a VPP, the assets can be forecasted, optimized, and traded like one single power plant.
In June 2021 Orange & Rockland Utilities of Rockland County and Sunrun, a US-based provider of residential solar electricity, announced that the companies have received approval from the Public Service Commission to deploy rooftop solar and battery systems as part of a VPP project. [14] This is an important development in moving New York State to its renewable energy goals and putting renewables on a level playing field with conventional fossil-fuel plants.
Beginning this year, Sunrun will bundle rooftop solar energy stored in more than 300 Brightbox battery systems and deliver it to the electricity grid when called upon by O&R. By bundling and coordinating the energy stored in Sunrun’s Brightbox home battery systems, Sunrun will form a virtual power plant to partially offset demand on O&R’s electricity grid in key areas, while providing clean, reliable, locally-generated solar power to residents in Orange and Rockland counties.
We need other utility companies to implement virtual power plants, and we need small-scale solar projects to participate in these virtual plants.
What’s Needed to Make More Small-Scale Solar Happen
Homeowners & Businesses: Extension of the Federal Investment Tax Credit. As part of the Inflation Reduction Act passed by Congress in August, the federal solar tax credit, also known as the investment tax credit (ITC), was increased to 30% and extended to 2034. For the next 10 years, homeowners can deduct 30% of the cost of a solar system from their taxes (this includes systems installed in 2022). In 2033 and 2034, the solar tax credit will be reduced to 26% and 22% respectively and eliminated in 2035.
Businesses can also claim the 30% solar tax credit but only until 2025. [15] There are many commercial properties that are suitable for small-scale solar, such as parking lots of shopping malls. The ITC for businesses must be extended past 2025 as an incentive for these businesses to install solar. However, one piece of good news is that the ITC can now be claimed by businesses that do not pay federal income taxes, e.g., non-profits. [16]
Solar Canopies in Parking Lots: Increased marketing to commercial property owners, and additional incentives. Owners of large commercial properties such as shopping malls should be made aware of the potential for solar canopies in their parking lots. A study from 2020 identified the potential of a number of parking lots in New York state, especially in Lower Hudson Valley [17]. Owners of other properties such as those identified by the Dr. Perez study [11] should also be encouraged to consider solar installations.
Other incentives in addition to the ITC should include assistance in the cost of connecting to the distribution grid. This cost can be substantial and has doomed many projects. Since the NYSIO grid is old and was not designed for distributed generation, grid upgrades are often required to interconnect small-scale projects greater than 1 MW, the entire cost of which falls on the developer and customer. Under existing rules, the first developer necessitating the upgrade had to bear the full cost, with only potential reimbursement from future projects to relieve that burden. In response, the PSC has adopted a new cost-sharing methodology which covers new distributed generators and energy storage systems of 5 MW or less, but it should cover larger systems, up to 15 MW. Although it should reduce upfront costs for these projects, individual cost allocations will need to be carefully reviewed to ensure utilities are acting fairly. [17a]
Upgrades to the distribution grid so it is compatible with renewables. Small-scale solar installations must connect to the distribution grid (rather than the transmission grid) because of their relatively low output voltage. Electricity on the distribution grid generally flows in only one direction, from centralized generators to substations and then to consumers. With distributed generation (DG), power can flow in both directions, but the distribution grid was not designed to accommodate widespread DG and this two-way flow of power.
Generation and demand in the electric grid must be closely matched. Maintaining acceptable voltage levels at all points along a distribution feeder is a fundamental operating requirement of all electric distribution utilities. Fluctuating power generation from distributed solar, for example, can impact the operation of any voltage regulation devices and complicate the task of maintaining voltage levels within regulated limits. The intermittency affecting solar energy production (e.g., cloud variability) may accelerate cycling of voltage regulation equipment which in turn results in increased wear and tear of such equipment. [18,19]
A distribution circuit can accommodate a certain amount of DG, without problems of any type, with no upgrades to the circuit. Thus residential rooftop solar (typically .5 kW or less) can be connected relatively easily. But installations with larger capacities (e.g., 1 – 15 MW) require modifications to the grid such as various circuit upgrades and/or the use of advanced inverter functions. These upgrades can be expensive (see 2) above) and time-consuming. [18]
In addition to hardware changes needed for the grid, traditional distribution and transmission planning does not address the benefits and challenges of DG systems. Quantifying the ability of distributed solar to reliably help meet electricity demand can be challenging. Additionally, traditional distribution planning procedures use load growth to inform investments in new distribution infrastructure, with little regard for DG systems and for solar development. [18]
Additional funds in the form of grants and/or subsidies should be made available to utilities to address these challenges.
A list of references for this article is here.