Charging EV’s with Solar PV’s & Batteries
The charging of electric vehicles (EV’s) with solar photovoltaic panels (PV’s) requires careful attention to both how PV panels are wired together and what the chargers are that are required to provide excellent quick charging services. In addition, sufficient battery capacity is needed to meet any demand peaks in the daytime and to cover any charging requirements when the sun is not shining. The high cost of batteries in the past made this a less than practical solution to achieve true zero emission vehicle charging. The introduction of iron air and sodium ion batteries now offers the potential to provide large quantities of storage capacity on-site that will allow recharging to occur from solar in the day and batteries at night and in bad weather. We will outline below both the evolving state of PV to EV interconnection and the development status of advanced batteries as well as supplements to batteries if additional peak capacity is required.
Solar PV Direct to EV Charging or Housing = Economic Advantages a\
Moving PV & battery capacity directly to loads on the same site have very significant impacts on economic returns and carbon emissions but also requires adding in several layers of supply and current management to meet the demands of vehicle quick charging stations. While is is a very new area of EV quick charging with little or no competition, proper entry into the market with high quality charging equipment and the right combination of power supply will be essential. Equally important is the goal of achieving real zero emissions which will require a mix of approaches for each supply option and in accounting for power losses at the delivery point. However, the economic rewards make this effort more than worthwhile given both the price paid for electricity sold to the grid by utility scale solar farms and the cost and resale value of electricity at a quick charging station or for on-site buildings or in areas where community solar is allowed (tribes, CO, CA & NM). Returns on invested capital can be up to 8 times higher than simply selling PV electricity to the grid and the wait time for inter-connection is likely to much shorter because of community benefits and reduced permitting opposition. The slide below shows examples of both utility bid pricing for solar electricity and retail prices for EV charging:
This affects the ability of Solar PV developers to make a profit. If all development is sold into the grid and developers have to wait 5 years before they can interconnect, this results in high overhead and interest borrowing costs. In addition, about one third of the projects never get built because of delays in permitting and interconnection. At least half are delayed, even when accounting for the 5 year wait. In the case of direct charging or use of electricity in the same location or through community solar, the wait will be much shorter and will allow for stepped up development of many sites starting at 5 MW and moving to 50 MW capacity. This means both much greater return on investment because of the higher prices realized above vs. a utility bid but also because the sales of electricity occur much more quickly because of the easier path to project approval and start up of electricity sales, EV charging, direct building loads and community solar. One MW hour of electricity sold to the utility is only worth $50 while the same electricity sold direct for EV charging is worth $680. At 13 times more sales revenue, it does not take long to recover utility scale PV investments. The slide below shows the potential benefits in terms of return on investment and the ability to attract capital for project build-out:
So if the economics are so favorable then why isn’t everyone doing it? Most EV charging has not gone into locations where there is room for EV charging and few of the EV charging sites are permitted to add large solar arrays. A few EV’s on the roof of a parking slot may be sufficient to recharge one car overnight. But our focus is to recharge a large number of cars to start and then to build up sufficient solar capacity to recharge electric trucks as they start hitting the highways in large numbers in 2027-28. Without a solar PV array at the same site the charges for electricity from the grid are very high for charging stations. This is because there is both the energy cost, a transmission and distribution charge and a demand charge to account for the added equipment needed to manage the peak draws of electricity. This translates into electric costs in the 30-40 cent range per kWh which is why retail rates can be as high as $0.68 per kWh (Flying J). This then results in only normal margins when electricity is resold from the grid. (buy at 25 to 40 cents and resell at 40-68 cents/kWh). This is why quick charging retail prices are high. You only get into the very large margins as detailed above if you move electricity directly from a utility scale solar system to a direct charge station and meet most or all of your load from solar or wind and batteries on site. This requires detailed planning that GCarbon Coin is currently undergoing in developing this project and the right sites with land for solar and that is near highway exits suitable for EV charging (and with room for housing or tourist facilities). This type of synergistic thinking is not normal in our specialist culture and requires careful evaluation and permitting of suitable sites and smart permitting processes to get regulatory approval.
REQUIREMENTS TO PROVIDE A RELIABLE & POSITIVE EV CHARGING EXPERIENCE
There are several steps needed to both compete as a quick charge station and provide the electricity from PV and batteries with high reliability. Most of the details are a bit proprietary so we will only give a general overview. Most of the general description below is only what is occurring in the charge industry anyway as it evolves from a less than perfect charge experience a few years ago to more sophisticated and user friendly experiences. The key is to learn how Tesla and some of its closest competitors have solved the technical issues and incorporate those in the EV charging network.
•All stations will use Nacs dc fast charge tesla or NBB chargers compatible for all ev’s
•We will follow ISO 15118 which governs the interface between charger & electricity
•180 to 250 kw dc charge system is easily compatible with power from pv’s & batteries
• Expected charge time per vehicle will be about 20 to 30 minutes now but expected to be 10 minutes for cars, which offers opportunities for other sales to motorists to increase profitability per station but provides rapid charge for more electric sales,
COMPETING ON BOTH PRICE AND SERVICE
Charging costs at quick charge stations vary a lot at this time because of limited competition and high pricing for electricity with some utility service providers. Flying J has the highest prices for charging trucks and cars at $0.68 per kWh but provides a full service truck stop to justify the higher cost. Circle K is just a convenience store so charges less and initial charging stations are in states with low utility rates or demand charges. We expect to sell electricity for charging at $0.34 per kWh. This will provide high margins if all of our electricity is provided in-house. If we have to buy electricity from the utility and pay demand charges margins will be smaller. We will avoid this by overbuilding PV capacity and through addition of lots of batteries.
The more important variable is meeting high levels of service and having a charging experience that matches the best Tesla or other competing stations. This requires utilizing the latest smart phone integration with chargers and the communication between charger and customer during the entire charge cycle. Other innovations will involve pass through design for stations so cars can be moved forward with buyer permission without having to go back out to the charging port (via a charging port manager). Couples will all be NACS ev compatible and meeting J3400 TM standards but all other optional features that make Tesla the preferred charging option will be duplicated as chargers all evolve to a common high standard. This includes notification when charging is at 80% and 85%, touch screens to adjust charging details and auto pay screens to make payment easy. Some features are listed below:
Lots of charging ports and easy in & out will maximize revenues and insure ports are always available
TECHNICAL ASPECTS OF LINKING SOLAR PV TO EV CHARGING
Charging infrastructure for quick charge of EV’s will be built up gradually based on demand at each station. However, the initial permitting and layout and installation of underground cables will consider the full build out plan so that it is easy to go from 5 ports to 10 ports by only adding charging ports. Likewise the build out of solar PV capacity will be planned in considering maximum demands for electricity for electric vehicles including cars and trucks and local demand from housing and community solar. At the same time, capacity will be added in modular increments to match expected demand in the next year and increasing number of electric vehicles and trucks actually getting registered and on the road.
The optimum build out goal for EV charging is 50.000 KWH of solar PV production with 8 MW load capacity. This will allow for charging of both cars and trucks and provide minimal requirements for grid electricity. We expect to build out to 6 to 10 charging ports at each station for cars and a similar number for trucks. Car ports will go in as soon as permits are obtained and ports for trucks will be installed as the number of electric trucks starts to climb to numbers that require a network of truck charging ports. Electricity sales are 9 times greater for trucks versus cars so we plan on focusing on this market segment as there is little competition and a strong interest by trucking fleets and freight carriers to have this capacity in place as they start to buy electric trucks.
Integration of Solar PV and EV charging demand will be important to insure steady flow of power based on projected demand for both cars & trucks. PV panels will feed to the DC bus that feeds the batteries & then EV’s. LTSPICE software will be used to model and control the input and output voltages of step-up converters that provide a bridge between a solar farm and a DC fast-charging station. We will use Tera 184 high capacity charger with 180 kw of output delivered with 400 amp cables. A 500 KW (500 kva) electrical panel will provide a connection between the PV array & grid to allow both emergency feed in to the grid and to draw electricity from the grid if we do not have enough Solar PV and battery capacty. Lincoln Electronic EV specific switch gear will also be installed. Management of equipment will be done using Distributed Maximum Power Point Tracking (DMPPT) controls. PV panels are used to feed the DC bus that feeds the batteries & then EV’s. LTSPICE software is used to model and control the input and output voltages of step-up converters that serve as a bridge between a solar farm and a DC fast-charging station. The software controls the flow of electricity from the PV panels to the DC bus that feeds the batteries &then EV’s. LTSPICE software will be used to model and control the input and output voltages of step-up converters that will bridge between the built up voltage and amperage from solar farm and vehicle requirements in the DC fast-charging station. This will insure that the maximum amount of PV powered and battery stored electricity moves to the charging station to meet load requirements. Some aspects of the full build out are illustrated below:
Solar PV panels & DC/DC step up converters will be used to reach 920 V in series & then parallel runs will be used to meet 400 A current required for quick charging. A battery buffer will manage fluctuations in current and will provide power when there is no sun. A DMPPT method will be used to reduce the decrease in output power caused by incompatible operating circuits and identical modules which will be added in series to meet the required voltage and then parallel identical rows to meet Amp requirements for vehicle charging. Charging for trucks will be more challenging and will be undertaken only once we have good operating systems for car charging. It will be based on same system design. Technical aspects of the design are pictured below:
BENEFIT OF BATTERIES & MICROGRID TO IMPROVE RELIABILITY OF OWN SUPPLY AND GRID STABILITY
The development of Solar microgrids with wind where appropriate and lats of large new tech batteries will provide both a reliable microgrid but also improve the overall grid stability in extreme weather. Most of the wiring of the solar PV array will not have the exposure to weather of transmission towers and distribution lines that can often short out the whole grid in extreme weather. The large iron air or sodium ion battery bank will also have a large reserve of power that can be drawn in in a powre emergency. These benefits will assist in getting utility interest in the facility and in allowing interconnection to the grid. These same features will also improve the reliability of our micro-grid so we can provide solar PV electricity to people needing to recharge electric cars or that are connected in the immediate area of the project. There are various ways we can combine renewable solar and wind and batteries to provide both local micro-grid and utility grid benefits:
Battery Ramping: When our local demand is greater than solar supply (or wind on site), the gap can be filled by batteries charged during sunny daylight hours. This will be done on a very large scale to meet the high power and energy requirements of EV quick charging and to a lesser extent peak demands in homes nearby. Batteries will be able to provide power extremely fast (known as ramping). In CA electric grid (CAISO) batteries provided 8 GW over 5 hours in Dec. 2023, when batteries provided the majority of ramping capacity. We will be doing the same thing but on a daily basis to meet vehicle power demands and on an emergency basis through a feed in to the utilities.
Response Time: Batteries will provide rapid response time because they can be charged and discharged to support real-time EV charging a housing needs due to thei much faster discharge capability versus pulling from the grid.
Stability Services: Batteries will provide to the micro-grid critical stability services such as frequency, voltage, and reactive power regulation, which will help the micro-grid maintain its ability to deliver electricity locally within safe windows of tolerance during regular operations. We can also provide emergency service to meet requirements of the utility grid such as the Sept. 6, 2023 emergency of ERCOT) when it was in a level 2 Energy Emergency Alert stage.
Utility Black Start: Batteries will be made available to the grid after a blackout, (called “black start”) This restoration service will bolster the resiliency of the grid, Our large battery capacity to meet EV charging and local homes can be switched to meet this black start requirement to improve grid reliability.
