Assessment of Solar PV for Residential Use
Introduction
Solar PV.
Renewable resources have been gaining traction in today’s energy demands. The most popular among these resources are the solar PVs in which most households have access to. In the Philippines, through the Renewable Energy (RE) Act of 2008, the use of solar PVs is encouraged by establishing the Net-Metering[1] scheme. Under this scheme, every grid connected household and commercial establishments with PV capacities up to 100kW can now partly satisfy their electricity demand by themselves and sell their excess power to the grid. The biggest hurdle to the access of solar PVs is the upfront cost. As a rough estimate, most PV system nowadays cost about Php 100,000.00 per kW capacity.
The objective of this study is to present a levelized cost of electricity (LCOE) of owning a grid-tied solar PV. In addition, simulations are conducted to identify the optimal solar PV capacity for the users’ existing electricity demand.
Computer-Aided Simulation
The study utilizes the Homer software for calculation and optimization of residential grid-tied solar PVs. Figure 1 shows a typical model for a solar PV system in a residential setting.
Figure 1. Homer Model for Solar PV System
A. Grid
The grid represents the local electricity distribution utility in-charge on an area of franchise. The electricity rates applied in this study is based on the 2017 energy rate[2] for residential customers under the Visayan Electric Company(VECO). The generation rate is based on the February 2018 net-metering rate[3].
B. Residential Load
The residential load used in the study was based on the sample load profile provided in Homer scaled on an annual average daily energy of 30kWh/day. The peak demand for the residential load is 4.1kW.
Figure 2. Residential Load Profile
C. Solar PV
The PV applied are polycrystalline panels with a peak capacity of 255WP per module.
Figure 3. PV Cost and Specifications
D. Converter
The inverter sizes are based on market availability. Table 1 shows the sizes considered for converter and PV.
Table 1. PV and Converter Sizes
Figure 4. Converter Cost and Specifications
Most of the cost calculations in this study are based on an actual project located in Cebu City. The capital cost field is based on 30% of the total project cost (replacement cost field). The O&M cost per year is based on a bank financing scheme with loanable amount of 70% of the total project cost at 6.5% per annum for 5 years. For study purposes, the loanable amount value with interest is spread throughout the 25-year period and applied with an inflation rate of 4%.
Simulation Results and Discussions
Different combinations of resources based on the considered capacities of PVs and inverters were simulated using Homer. Cost Computation table shows the cost comparison for each resource combination. It can be inferred from the table that the cost of electricity decreases with increasing PV capacity. However too much PV capacity could be inefficient. As shown in Cost Computation table, the cost of electricity starts to increase from the minimum COE 8.541₱/kWh to 8.588₱/kWh for PV capacity greater than 14.28kW, that is 18.87kW. This is particularly true since the generation rate is only around one-half of the electricity distribution rates. The PV capacity of 18.87kW has more excess energy sold to the grid compared to the 14.28kW PV capacity.
Selecting a PV capacity roughly around the peak demand has very little impact to the electricity cost. A 4.59kW PV capacity with an inverter capacity of 3.9kW, as shown in Cost Computation table, for a peak demand of 4.1kW has a COE of 9.75₱/kWh as compared the average distribution rate of 10.93 ₱/kWh, a 10.8% reduction. A PV capacity of at least 50% more than the peak demand can decrease the COE dramatically. This is evident on the 6.12kW PV capacity with an inverter capacity of 3.9kW. This reduces the COE to about 17.3% to 9.05 ₱/kWh.
It is interesting how much inverter capacity should be paired with the selected PV capacity. The Cost Computation table also shows the optimized inverter capacity for each PV capacity. It can be seen that the optimal inverter capacity varies from 35% to 65% of the PV capacity.
Figure 5 shows mean power values for an actual 3.825kWp PV system. It can be seen that the highest power generation occurs in the months of March to June. It is also worth noting that power generated above one-half of the system capacity runs only for 22 hours in one year.
Figure 5. 3.825kWp Mean Power Values (kW)
Conclusion and Recommendation
Solar PV systems presents a great potential to decrease the electricity cost for each household. With careful planning and design considerations, an average household can save as much as 21% of the electricity costs. The choice of the Solar PV system capacity is very significant to achieve maximum savings. Based on the findings of this study, it is recommended to have a PV capacity about 1.5 to 4 times the existing peak demand while selecting an inverter capacity between 35% to 65% of the PV capacity.
Reference/s:
[1] “Net Metering Home”. Retrieved March 12, 2018, from https://www.doe.gov.ph/net-metering-home.
[2] Average Residential Monthly Rate. Retrieved March 12, 2018, from www.visayanelectric.com.
[3] February 2018 Net-metering rate. Retrieved March 12, 2018, from www.visayanelectric.com.
[4] “How to Finance Solar Rooftops”. Retrieved March 12, 2018, from https://www.doe.gov.ph/6-how-finance-solar-rooftops.
[5] SUNNY BOY 1300TL / 1600TL / 2100TL Data Sheet. Retrieved March 12, 2018, from http://gold-coast-solar-power-solutions.com.au.
[6] TSM-PC05A TSM-PA05A Data Sheet. Retrieved March 12, 2018, from https://www.sunergysolar.com.au
[7] Cebu Max, Min and Average Temperature. Retrieved March 12, 2018, from https://www.worldweatheronline.com
