## the equivalent relationship of power – Global Homework Experts

1. Determine the energy required at night, whether or not intelligent feature detection and directional lighting are activated

The road lighting standards are shown in the following table:

According to the light level standard and the equivalent relationship of power, the LED lighting power is set to 50W, and the subsequent calculations are designed with 50W.

https://www.waveformlighting.com/home-residential/what-is-the-difference-between-lux-and-lumens

https://www.any-lamp.com/blog/lumen-and-lux

When smart lighting is not enabled:

Assuming that the working time at night is 12h and the power is 50W, according to the given data we can know that the total energy consumed in a day is:

The energy consumed by the above calculation is all from the solar energy generation during the day, it can be assumed that the lighting changes from 6:30AM to 6:30PM (12-hour interval), the photovoltaic cell works for twelve hours a day, and the power generated by the photovoltaic panel is semi-sinusoidal, according to these given conditions we can get the energy emitted by the photovoltaic panel in a day is:

Where the Ppv peak is the peak power of the photovoltaic, according to the photovoltaic power generation is equal to the consumption of the load, then we can find the peak power of the photovoltaic cell is:

For the day’s working conditions, the peak power of photovoltaics can be obtained to be about 78.54W

When smart lighting is enabled:

Assuming that the working time at night is 12h, the power is 50W, due to the intelligent detection of passers-by and vehicles, it is assumed that the effective working time coefficient is k, and the value range is 0-1, so that the k value is 0.5, that is, the effective working time of the LED is 0.5 * 12h = 6h. According to the given data we can know that the total energy consumed in a day is:

The energy consumed by the above calculation is all from the solar energy generation during the day, it can be assumed that the lighting changes from 6:30AM to 6:30PM (12-hour interval), the photovoltaic cell works for twelve hours a day, and the power generated by the photovoltaic panel is semi-sinusoidal, according to these given conditions we can get the energy emitted by the photovoltaic panel in a day is:

Where the Ppv peak is the peak power of the photovoltaic, according to the photovoltaic power generation is equal to the consumption of the load, then we can find the peak power of the photovoltaic cell as:

For the day’s working conditions, the peak power of photovoltaics can be obtained to be about 39.27W

1. Depending on the geographical location and the overview of solar availability in winter, determine the size and orientation of the photovoltaic panels to provide the minimum energy

Latitude in Nottingham: 52° 57′ 13″ North Longitude: 01° 09′ 02″ West

On this website https://re.jrc.ec.europa.eu/pvg_tools/en/ analyze its relevant lighting information. Using the lighting data of the whole year of 2020 for analysis, the inclination of the photovoltaic panel is set to 75°, and the data of the optimal angle and the set angle are observed for comparative analysis.

The collated data is as follows:

Through the analysis of the whole year, it can be seen that the light radiation energy in December is the smallest, and the light radiation energy of the whole month under the condition of 75 ° is about 46.09kWh/m2, which can be seen that the setting angle of 75 ° in winter is greater than the optimal angle of the system recommended by the system. At this time, the average daily power generation is about 46.09 kWh/m2/30d = 1.536kWh/m2.

From this, the area of the required solar PV panels can be further calculated:

It was finally determined that the size of the photovoltaic panels was about 0.39m2, the direction was south-facing, and the tilt angle was about 75°.

LED street lights are adjusted without intelligent detection enabled:

The voltage across the design cell is 380V, and according to the all-day power generation power of the photovoltaic cell calculated above, it can be simulated using the energy exchange simulation model of the battery and the photovoltaic cell throughout the day.

Without enabling the adjustment of intelligent detection, the peak photovoltaic power generation power at this time is 78.54W, the power generation time is 6:30 a.m. to 6:30 p.m., the load power consumption is LED 50W, and the working time is designed to be 12h, which is 6:30 to 6:30 a.m. at night. Set these two parameters to the corresponding simulation model.

Figure 1 Praxair photovoltaic cell model

The battery voltage is set to 380V, and the relevant parameters are substituted into the simulation model, where the Pload _peak = 50W, Pload_off = 0W The parameters of the parameter model after the substitution are substituted into the given simulation model.

PV_peak_power=78.54

Run a simulation to observe the relevant output waveform. The following figure shows the peak power of photovoltaic cells and the waveform of one-day power generation.

Figure 2 Photovoltaic cell peak power and one-day power generation waveform

As can be seen from the above waveform, the maximum power of PV at this time is consistent with the design, which is 78.54kW, and the power generated by the photovoltaic cell in twelve hours during the day is 0.6kWh, which is consistent with the output of the design. At this time, the daytime power generation of the photovoltaic cell is equal to the energy consumed by the load all day, and the energy consumed by the load throughout the day comes from the daytime power generation with the photovoltaic cell.

Figure 3 Photovoltaic cell power and two-stage load waveform

It can be seen from the figure that the LED load at this time has an action time of 6:30 pm to 6:30 am, and the load consumption power at this time is 50W, which is in line with the design expectations.

The following figure shows the power of the battery charge and discharge and the power curve waveform.

Figure 4 The power of the battery and its energy

The above figure shows the power of the battery and the waveform of its energy fluctuations, as can be seen from the power waveform above, the peak output power of the battery is about 78.54W, which is the peak power generation power of photovoltaics. The following figure is the Ah energy waveform of the energy storage battery, and it can be seen from the figure that the maximum value occurs around 18:30 pm at this time, and the peak Ah at this time is 275 Wh. The corresponding point of discharge capacity is 6:30 in the morning, which is about 325Wh at this time, which is consistent with the photovoltaic power generation and load consumption of 12h. That is to say, the maximum capacity of the battery should be selected for the capacity standard of 600Wh.

The following figure is the Ah curve of the battery, as can be seen from the figure, the maximum discharge Ah is 0.855Ah, and the battery capacity requirements are not very large. Therefore, in the process of actually selecting the battery, you can choose a lithium battery of 12V2Ah.

Figure 5 Curve of charge and discharge Ah of energy storage battery over time

LED street lights are adjusted without intelligent detection enabled:

The voltage across the design cell is 380V, and according to the all-day power generation power of the photovoltaic cell calculated above, it can be simulated using the energy exchange simulation model of the battery and the photovoltaic cell throughout the day.

Without enabling the adjustment of intelligent detection, the peak photovoltaic power generation power at this time is 39.27W, the power generation time is 6:30 a.m. to 6:30 p.m., the load power consumption is LED 50W, and the working time is designed to be 12h, which is 6:30 to 6:30 a.m. at night. Set these two parameters to the corresponding simulation model.

Figure 1 Praxair photovoltaic cell model

The battery voltage is set to 380V, and the relevant parameters are substituted into the simulation model, where the Pload_peak = 50W, Pload_off = 0W.

PV_peak_power=39.27

Run a simulation to observe the relevant output waveform. The following figure shows the peak power of photovoltaic cells and the waveform of one-day power generation.

Figure 2 Photovoltaic cell peak power and one-day power generation waveform

As can be seen from the above waveform, the maximum power of PV at this time is consistent with the design, which is 39.27W, and the power generated by the photovoltaic cell in twelve hours during the day is 0.3kWh, which is consistent with the output of the design. At this time, the daytime power generation of the photovoltaic cell is equal to the energy consumed by the load all day, and the energy consumed by the load throughout the day comes from the daytime power generation with the photovoltaic cell.

Figure 3 Photovoltaic cell power and two-stage load waveform

It can be seen from the figure that the LED load at this time is acting from 6:30 pm to 6:30 am, and the load consumption power at this time is 50W, which is in line with the design expectations.

The following figure shows the power of the battery charge and discharge and the power curve waveform.

Figure 4 The power of the battery and its energy

The above figure shows the power of the battery and the waveform of its energy fluctuations, as can be seen from the power waveform above, the peak output power of the battery is about 39.27W, which is the peak power generation power of photovoltaics. The following figure is the Ah energy waveform of the energy storage battery, from the figure, it can be seen that the maximum value occurs at about 18:30 pm at this time, and the peak Ah at this time is 187.5Wh. The corresponding point of discharge capacity is 6:30 in the morning, which is about 162.5Wh at this time, which is consistent with the photovoltaic power generation and the 12h power consumption of the load. That is to say, the maximum capacity of the battery should be selected for the capacity standard of 300 Wh.

The following figure is the Ah curve of the battery, as can be seen from the figure, the maximum discharge Ah is 0.427Ah, which is not very demanding on the battery capacity. Therefore, in the process of actually selecting the battery, you can choose a 12V1Ah lithium battery.

Figure 5 Curve of charge and discharge Ah of energy storage battery over time

Battery selection and related calculations

Batteries are generally connected in series applications, so at this time only calculate the number of series connections of the cells, according to the battery is directly paralleled to the photovoltaic panel, that is, Vbus voltage 380V.

Energy storage batteries can be divided into a variety of types, common lithium batteries, lead batteries two categories, these two types of batteries have their own characteristics. Lithium batteries are mainly high power density, high cost, long life, and small size. It has been widely used in photovoltaic microgrid systems. This design selects lithium battery, and the grade voltage is selected as 12V.

Actually take 32 48V batteries in series. According to the simulation results, consider a certain margin to choose a lithium battery with 2Ah.