Optimum Utilization of Electric Circuit Capacity by Adding Electric Vehicle Charging

Abstract

This invention enables Electric Vehicle (EV) charging requirements to be supplied by electric power available off-peak without increasing demand charges. It does this by continually measuring primary loads and enabling EV charging to utilize only that power that will not increase total demand. Grouping software available from Electric Vehicle Service Equipment (EVSE) suppliers allows the available power to be shared among multiple vehicles.

Claims

1. A system comprising; Communication equipment and specialized control software to control operation of a group of Electric Vehicle Service Equipments (EVSEs), A group of Electric Vehicle Service Equipments (EVSEs), which provide electric energy recharging facilities to one or more Electric Vehicles, A source of electric energy supplying a building or other facility, A current tap to provide electric energy to the group of EVSEs from the source of electric energy, An electric energy meter to measure the electric power load on the source in kW, and Software to enable recharging of the electric vehicle(s) without increasing the measured demand on the source of electric energy,

2. The system of claim 1 in which an additional electric energy meter is installed to measure the electric power load on the building, exclusive of the power consumed by the EVSEs.

3. The system of claim 1 in which the communication is via a WiFi internet router.

4. The system of claim 1 in which the communication is via a cellular phone connection.

5. The system of claim 1 in which the software is resident in an on site microcontroller.

6. The system of claim 1 in which the software is resident in the cloud.

7. A method comprising; Installing and operating the system of claim 1 in which a current tap is installed so as to provide electric energy from a source of electric energy to a remotely controlled group of EVSEs, the EVSEs are controlled remotely as a group and their power level can be limited to an amount of available limiting power, designated A, the value of A is transmitted to the group periodically to enable the EVSEs to equally recharge whatever electric vehicles are plugged in at a maximum rate that will not increase electric energy demand on the source of electric energy measured as M, by an electric energy meter, The total system load is limited to the maximum monthly billable demand of the primary load, designated L, by maintaining A<(L-M), and L is updated each monthly billing cycle by recording M at suitable intervals and changing L to the maximum M measured during the month.

8. A method comprising; installing and operating the system of claim 1 in which an electric energy meter is installed to measure only the primary load on the source of electric energy, designated M, The current tap is installed so as to provide electric energy from the source of electric energy to a group of EVSEs, which energy is not measured by the current transformer, the EVSEs are controlled remotely as a group and their power level can be limited to an amount of available limiting power, designated A, the value of A is transmitted to the group periodically to enable the EVSEs to equally recharge whatever electric vehicles are plugged in at a maximum rate that will not increase electric energy demand on the source of electric energy, The total system load is limited to the maximum monthly billable demand of the primary load, designated L, by maintaining A<(L-M), and L is updated each monthly billing cycle by recording M at suitable intervals and changing L to the maximum M measured during the month.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic diagram showing the system of this invention applied to a building with a metered electric energy supply and added EVSEs.

[0021] FIG. 2 is a schematic diagram of software used by the system of FIG. 1 to achieve continuous evaluation of the amount or power available for EV charging and of the expected demand charge limit.

DETAILED DESCRIPTION OF THE INVENTION: THE PREFERRED EMBODIMENT

[0022] FIG. 1 shows a building 10 with electric distribution panel 12 supplied with electric energy from the electric grid through meter 14. EVSEs 22, 24 and 26 are grouped on circuit 28, which is controlled by the system controller 20 of this invention. Controller 20 reads current transformer 16 deployed between meter 14

[0023] and circuit panel 12 to measure the primary load on the circuit. Tap 18 prior to transformer 16 provides electric power to group 28, which is not measured by current transformer 16. Controller 20 comprises a microcomputer to run software to control charging in accord with this invention and communication equipment to communicate with WiFi router or cellphone connection to the Internet 40, which also communicates with EVSEs 22, 24 and 26. Electric vehicles 30 and 32 are plugged in to EVSEs 22 and 26 waiting for controller 20 to enable charging by transmitting an available power limit signal through router 40 to the cloud which will return charging signals distributing the available power equally to 30 and 32.

[0024] FIG. 2 is a schematic diagram of the software in controller 20, which controls EVSE group 28 and recalculates from month to month the demand charge limit. The program is started with an estimate of the demand charge limit L derived from previous month's electric bills. This is an estimated maximum demand for the primary loads of the building, which determine the demand charge leveled by the electric distribution company. As long as the demand measured by current transformer 16, M, is lower that the estimated demand charge limit, controller 20 sets the limit for the group of EVSEs at the difference between the measured primary demand M and the demand charge limit L. The EVSE cloud-based grouping software then splits up the available EVSE power A=L-M between EVs 30 and 32 which are plugged in ready to charge. In the early morning hours with low primary demand and few EVs plugged in they may be able to draw maximum power without increasing demand. At other times with more EVs or less power available above the primary needs, the group of EVSEs will share the available power, but in all cases the circuit will be providing the maximum power that can be used at the limiting power that is available and thus at minimum cost. The result is an increase in the efficiency of utilization of electric energy supply based on the ability of EVs to accept energy at variable rates and variable times without prejudicing the utility of the vehicles.

[0025] Controller 20 measures the demand for primary loads at suitable intervals such as the 15 minutes often used for demand charging. If the measured primary load is greater than the estimated limit, M>L, the limit will need to be reset upwards because next month's bill will show a higher demand. Also there is no room for EV charging and a signal to that effect is sent to Group 28.

[0026] If M is not greater than L, L<M, two actions are taken. First, the actual M readings are stored in a register for a monthly billing period and if all M for the month are lower than L the highest M for the month is the new (lower) L for the next month.

[0027] Second, L-M is the available power for EV charging, which is transmitted by controller 20 to group 28 as the new group limit. The EVSE group utilizes this available power to recharge the EVs in the most efficient manner. If there is enough power available and few enough EVs connected the EVs will be charged at maximum power. If there are more EVs or less power, the available power will be apportioned among the EVs by the EVSE supplier over the internet as they are programmed to do by the EVSE manufacturer The program then recycles to the next measurement M and comparison of M and L.

EXAMPLE

[0028] Starting with the configuration shown in FIG. 1 at midnight with an estimated demand charge limit L of 50 kW and a measured primary load M of 25 kW there is 25 kW of capacity to charge the two EVs connected, and each can charge at the maximum rating of the EVSEs of 10 kW. The total load, primary plus EVs, is 45 kW.

[0029] At 6 AM the primary load has risen to 35 kW and the controller 20 has signaled to the cloud-based grouping software controlling EVSE group 28 that the group limit is now down to 15 kW. The grouping software splits this between the two EVs and allows each to charge at 7.5 kW. The total load is 50 kW.

[0030] At noon the primary load is 40 kW and the group limit is 10 kW. If only one EV wants to charge it gets the full 10 kW. The total load is 50 kW.

[0031] At 6 PM the primary load is 50 kW, the group limit is zero and even though two EVs are back and plugged in, the EV group load is limited to zero, but the total load is 50 kW. The EVs will have to wait until the primary load drops enough to make some capacity available to them. However, they can readily do this since in the early morning hours they can accumulate as much as 60 kWh each, which will take them up to 240 miles each next day.

[0032] From this example one can see that although the primary load varies from 25 to 50 kW, a typical range from night to day, by means of this invention and the ability to manage group charging provided by the EVSE manufacturers, the overall load including EVs is almost constant but the demand charge is not increased. The cost of the extra 300 kWh of energy available to recharge the vehicles is just the cost of energy, and the minimum off-peak cost at that.

RELEVANT PREVIOUS LITERATURE

[0033] There are a great many US Patents and Patent Applications on the use of electric energy storage to manage peaks in demand and control demand charges. A number of inventors, Hooshmand, Moshlemi, Nakayama, Ashgari have assigned such patents to NEC, Princeton, N.J., USA. They are primarily concerned with the method of calculating the amount of offsetting power needed from a storage system to control demand charges.

[0034] Chiang describes managing charging strips so that the ones most in need are charged first and all are charged adequately, similar to group charging of Electric Vehicles.

[0035] Gow calculates a cost of energy and adds energy from storage if warranted.

[0036] Doorn allocates EVs to locations where grid power is most available

[0037] Chow measures energy consumed by primary loads and calculates an offset from storage to minimize demand charges.

[0038] None of the above disclose a system for measuring the demand of primary loads and filling in the gap with a tailored load which is the essence of this invention. While the drawings and descriptions in this application are intended to be comprehensive, it will be understood by those skilled in the art that there are similar means to achieve the same ends, which fall within the claimed scope of this invention.