Note: 1. All prices in this programme are in RMB Yuan.
2. The prices of products in this programme are all prices for project works in China, for reference in foreign projects, and are implemented according to local prices.
I. Technical programme
1.1 Overall programme
In the context of low-carbon living advocated by "Carbon Peak" and "Carbon Neutral", distributed PVs are installed on unused rooftops of homes and gardens, and energy storage units are configured to provide a stable power supply during the day and a continuous power supply at night. This is a new type of green, economical and independent micro-grid power supply model for courtyards.
Figure 1: System topology diagram
The Residential Green Power System supports two modes of off-grid power supply and grid-connected utility power supply, and the free and flexible combination of three modes of power supply: PV + energy storage + utility power. With the expansion of the new energy vehicle market, the Residential Green Power System can also work with home charging piles to realise an integrated PV+storage+charging pile power supply and consumption system, and the system can also be promoted and applied to industrial and commercial complexes, villas, PV carports and other application sites.
1.2 Equipment selection
1.2.1 Inverter selection
The inverter is the core conversion equipment of the PV system, connecting the DC side and the AC side, and it needs to have perfect protection functions and high quality power output. The selection of the inverter must meet the following requirements.
(1)High conversion efficiency
(2)Wide DC input voltage range
(3)High quality electrical output
(4)Effective means of protection against the "silo effect"
(5)Intelligent control of electrical energy tides
(6)Support Modbus CAN and other communication protocols BMS, MES communication flexibility
Table 1: Residential Green Power inverter parameters
|
PV String Input Data
|
|
Max. DC Input Power (W)
|
6000
|
|
Max. DC Input Voltage (V)
|
550
|
|
MPPT Range (V)
|
150-550
|
|
Start-up Voltage (V)
|
160
|
|
MPPT Nominal Voltage (V)
|
360
|
|
Max. Input Current Per Trackers (A)
|
13.5
|
|
Max. Short Current Per Trackers (A)
|
15.2
|
|
No.of MPPT Trackers
|
2
|
|
No.of Strings Per MPPT Tracker
|
1
|
|
AC Output Data（On-grid）
|
|
Nominal Output Power (W)
|
5000
|
|
Max. AC Output Power (W)
|
6000
|
|
Max. AC Output Current (A)
|
24
|
|
Output Voltage Range (V)
|
180-270
|
|
Nominal Output Voltage (V)
|
230
|
|
Nominal Output Frequency (Hz)
|
50/60
|
|
Output Power Factor
|
~1 (Adjustable from 0.8 leading to 0.8 lagging)
|
|
Output THDi (Nominal Output)
|
<3%
|
|
AC Output Data（Off-grid）
|
|
Nominal Output Power (W)
|
5000
|
|
Nominal Output Voltage (V)
|
230
|
|
Nominal Output Frequency (Hz)
|
50/60
|
|
Automatic Switch Time (ms)
|
≤10
|
|
Efficiency
|
|
Max. Efficiency
|
97.60%
|
|
Euro Efficiency
|
97.00%
|
|
MPPT Efficiency
|
99.80%
|
1.2.2 PV panel selection
The basic principle of PV module selection: under the premise of high technical maturity and reliable operation of the product, combined with the natural environment around the power station, construction conditions, and transportation conditions, choose the type of PV module that is dominant in the industry and the direction of technical trends. Taking into account module efficiency, technical maturity, market share and the choice available when purchasing and ordering, the overall development trend of PV modules is now that the single panel power is getting bigger and bigger and the efficiency is getting higher. The size of the PV panels and the ease of installation are also important factors in the selection of PV panels.
II. Application examples
2.1 Project requirements
A domestic customer in a certain area is currently supplied by the mains electricity supply, which is unstable and subject to power cuts at times, with a large difference in the price of electricity between peak and valley hours. It is now necessary to supply the building with electricity from a roof-mounted PV module, and to configure the batteries to store excess electricity from the PV and to supply electricity to appliances at night or during peak hours. The maximum household electricity consumption is around 12kW, with building appliances using electricity mainly during the day, with fan coils, refrigerators and other equipment using an average of around 4.5kW. At night the building uses less electricity, with a power of around 1kW. Peak electricity consumption is between the hours of 7:00 and 9:00 in the morning and evening. In addition to the electricity used by buildings, AC charging posts have a power of 6kW and new energy vehicles are usually charged at night.
2.2 Solutions
Designing integrated light + storage + charging solutions for household electricity. Using the roof of an unused building, PV modules are installed to supply electricity to the home. A lithium battery storage module unit is configured to store the excess PV energy and the nighttime utility power to discharge it during peak electricity consumption periods. The storage inverter enables intelligent piping of tidal currents. Timely charging of new energy vehicles.
Figure 2: Example of a Residential Green power application
The local light conditions are good, with about 10 hours of sunshine. Considering the demand for full consumption, the PV installed capacity is initially designed to be 5kWp, covering an area of about 25 square metres. The energy storage unit is mainly designed to regulate the output of the PV panels to promote full consumption consideration, while the storage battery uses the low price of electricity at night and the surplus PV power generation to discharge in the morning and evening hours from 7:00 to 9:00. The initial design of the storage unit is 10kWh, using two 5kWh modules, installed against the wall.
The inverter supports full storage mode, complete energy storage mode, priority storage and discharge mode, priority utility mode, etc.
2.3 Configuration list
Table 2: List of equipment configurations
|
Serial number
|
Equipment name
|
Specification
|
Unit
|
Number
|
|
1
|
PV modules
|
500W
|
only
|
10
|
|
2
|
Optical storage inverters
|
5kW
|
Terrace
|
1
|
|
3
|
Off-grid protection box
|
10kW
|
set
|
1
|
|
4
|
Installation management and consumables
|
|
|
|
|
5
|
Battery modules
|
5kWh
|
Terrace
|
2
|
|
6
|
AC Charging Posts
|
6kW
|
Terrace
|
1
|
Summary: 1) The construction scale of the project is 5kWp, and the construction investment cost is 31,000 yuan.
2) Unit cost 6.2 yuan /W, such as tiling 1240 yuan /㎡, such as scaffolding 775 yuan /㎡.
Note: 1. The estimated cost is the construction cost within China, and the actual construction risk and other costs shall be taken into account abroad.
2. The battery module and AC charging pile are not included in the cost calculation.
3. The battery module and AC charging pile configured in the chart cost 27,000 yuan.
2.4 Revenue analysis
2.4.1 PV revenue
Table 3: 25-year electricity generation estimates
|
Year
|
On-grid electricity (million kWh)
|
Year
|
On-grid electricity (million kWh)
|
|
1
|
8954.0
|
14
|
8213.7
|
|
2
|
8864.5
|
15
|
8164.4
|
|
3
|
8775.8
|
16
|
8115.4
|
|
4
|
8723.2
|
17
|
8066.7
|
|
5
|
8670.8
|
18
|
8018.3
|
|
6
|
8618.8
|
19
|
7970.2
|
|
7
|
8567.1
|
20
|
7922.4
|
|
8
|
8515.7
|
21
|
7874.9
|
|
9
|
8464.6
|
22
|
7827.6
|
|
10
|
8413.8
|
23
|
7780.6
|
|
11
|
8363.3
|
24
|
7734.0
|
|
12
|
8313.1
|
25
|
7687.5
|
|
13
|
8263.3
|
Total
|
206883.6
|
The local solar resources are good, with an annual radiation of 2107kWh/㎡, annual power generation = 2107×17%×25=8954kWh, total power generation of 206,000kWh in 25 years.
2.4.2 Energy storage benefits
The energy storage unit has two main charging and discharging time periods. A night charging, 7:00 ~ 9:00 am discharge, can be used as a supplemental power supply of the utility; a section using surplus PV charging, 7:00 ~ 9:00 pm discharge time period discharge, can be used as a supplemental power supply of the utility. Evening discharge gain is to promote the PV consumption, the gain is counted in the PV system, here consider the morning discharge gain.
5kW/h battery, average depth of discharge considered 85%, 8.5 kWh per day, 3102 kWh per year. The peak-valley differential price is taken as 0.7 yuan, with an annual electricity saving of 2171 yuan. The main function of the energy storage battery is the improvement of the electricity supply service, and the peak-valley differential gain is only its direct economic benefit.
