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Performance Analysis

Updated

SolarPlus has been the industry-standard, best-practice design solution to meet Australian requirements since its initiation in 2012 by Solaris Pty Ltd in partnership with the Australian Solar Council.

In 2017, SolarPlus introduced an advanced performance algorithm which provides best-in-class modelling across a broad range of design configuration options including grid-connect, hybrid/backup battery storage, off-grid, system upgrades and supporting a wide range of load profile and tariff analysis options.

The 2023 v5 update uses the Cubas cell equivalent circuit model. This modern and innovative method employs an analytical approach, leveraging explicit expressions and a new mathematical technique, the Lambert W-Function, to more accurately calculate the parameters of the solar panel’s equivalent circuit. This technique enhances the precision of solar panel performance analysis to better understand and model the behaviour of solar cells under various operating conditions.

 

 

Metrics, charts, and information available on the Design Review Page

 

Once the system has been designed by the user, SolarPlus evaluates the performance of the system based on certain key parameters that have been provided on the Contact, Energy and Design pages. These include:

  • Site Location      

  • Tariff rates                                        

  • Consumption Profile

  • Module Specifications

  • Inverter Specifications                 

  • Battery Specifications

 

 

Daily Average Energy

Solar consumed: How much solar energy is used on site. Includes new and existing PV.

Energy consumed: Total energy consumption at the site, regardless of source.

Battery consumed: How much battery energy is used on site.

Solar exported: How much solar energy is exported to the grid. This factors in export limits.

Grid supply: Energy from the grid used to supply loads.

Battery export to grid: Energy sent to the grid as programmed

Grid charge to battery: Grid energy used to charge the battery as programmed.

You can select between the annual daily average, or the daily average for different months of the year.

 

 

 

Self Consumption

This is the percentage of solar production that is used on the site, either to supply loads, or charge a battery. If the PV array is too large, and the load is small, or mostly at night, then the self consumption % will be low.

Self consumption = (Solar Production - Solar Export) / Total solar production * 100

 

Specific Yield

This is how much energy is produced for every 1kW of PV installed. Once you are familiar with the standard Specific Yield for your latitude, this is a useful metric for quickly assessing how well the solar is performing. Alternatively, you can refer to the Performance Ratio / system efficiency.

Specific Yield = Average PV energy production / PV array nominal power

 

Consumption vs Production by Month

SolarPlus, with its powerful computational features, provides users with critical information that helps them model their renewable energy systems to suit the demands of the property across an entire year. 

In order to evaluate the performance and energy yield of this system, SolarPlus takes solar data from within 10 km of your location and simulates a typical year of operation. This way, SolarPlus evaluates and provides the accurate statistics needed to forecast the energy available to meet the user’s energy needs and to charge their battery (if applicable).

The chart on the right highlights the daily averages per month for an entire year for a particular location of the energy generated using PV, energy consumed, excess PV energy exported, grid energy imported, and the Genset runtime or battery hours of autonomy, as applicable.

Note:

  • “Battery hours of autonomy” means how long the battery can provide energy to the loads in the complete absence of any other energy source (grid, PV, etc.)

  • The Genset runtime is displayed as total hours/month (not as daily average)

 

Toggling Average Daily Performance of the system across different time frames

SolarPlus offers a comprehensive feature on the Reports page, that assist the users in analysing the daily performance characteristics of the system.

This chart assesses how daily consumption is being met by solar power during the day and by the battery overnight.

By selecting the time range and the month for evaluation, the user can analyse the impact of different energy systems. The graphic here provides a user-friendly interface, wherein, the user can toggle (on/off) between different energy systems to highlight the influence of the system on balancing the energy needs of the location.

The graph here highlights the performance of different systems across a single day (24-hour time frame) and highlights the periods of solar generation and export (in yellow) while displaying the influence of battery storage(in green) on the system balance.  The grid supply is highlighted in grey signifying the import of electricity from the grid. 

The user can also generate other charts by selecting different time frames (monthly, daily, yearly) and clicking the blue ‘Generate Chart’ icon.

Likewise, the user can analyse different sections of the energy system, by toggling across various features in the system in the Reports Section of SolarPlus.

 

 

When looking at this chart, it is recommended that users set the time range to week view and check the chart for different months (for example, January to check summer performance and June to check winter performance). Drilling down to the weekly views of different months can help users check the system performance including battery charge/discharge cycles across the specified week.

Multiple time range options are available:

  • Day view for day entered

  • Week view starting the day and month entered

  • Year average week - an average week in the year

  • Month average day - an average day in the month entered

  • Year average day - an average day in the year

  • Year-end average day - an average day in the period Dec - Feb (summer for AU/NZ)

  • Mid-year average day - an average day in the period Jun - Aug (winter for AU/NZ)

  • Full-year hourly - the main purpose of this chart is to allow users to export hourly data of the modelled system

 

 

Battery performance graphics – Impact of storage on system performance

The infographic here portrays the differences in peak demand across each month of the year with different systems. Consumption patterns in comparison with solar, solar, and storage, provide valuable information to users to model their systems, to enhance both monetary and environmental savings.

Other key information like battery capacity, depth of discharge(DoD), Battery cycling,  battery lifetime, and energy costs are also provided for further, in-depth analysis.

Battery energy cost relates to the cost of energy supplied by the battery module, calculated using the price of the battery module, the cost of the avoided grid energy, and the price of the feed-in tariff that may have been foregone in order to charge the battery. This metric does not take into consideration the price of the battery inverter or hybrid inverter, and therefore is not calculated for all-in-ones.

 

Expected Financial Savings Breakdown – Before and After system installation

The solar power system can help users save on bills. The first chart shows possible electricity tariffs before and after. The second chart shows financial benefits including tariff savings, export earnings, and incentives.

Based on the energy tariffs and the consumption profiles uploaded to the system on the ENERGY page of the workflow, SolarPlus calculates the financial savings that the user may be entitled to, after the installation of the system.

SolarPlus, utilising key information such as Feed-in tariff (FiT) and peak electricity charges, determines the individual variations in prices before and after the installation of the systems, for peak, off peak, and shoulder time frames in the energy consumption cycles.

In addition, SolarPlus also determines the yearly benefits that the user might be entitled to, through solar exports, incentives, and tariffs. All this information, provided on the Reports page, serves great value, in assisting the customer, to understand the benefits of the proposed renewable energy system.

 

 

 

 

 

Battery Backup Hours

SolarPlus uses the average day in winter to model the battery cycling against consumption and solar to check for the length of autonomy before fallback to the generator.

The backup hours are displayed for an average day in the month selected and the discharge time setpoint.
The graph can be interpreted as “the number of hours the battery can provide to the loads for an average day in the month once the battery starts discharging at a certain time of the day”.

Although the lifetime of a battery is conditional on the demands that are put on it, the degree to which it is recharged, and environmental factors such as temperature, SolarPlus offers advice on maintenance procedures and suggest a maintenance schedule to help extend the battery life to the maximum.

 

Financial Investment Standpoint and ROI metrics – Yearly Cashflow and Payback time

SolarPlus compares a projection of expected electricity costs with the accumulated savings after investing in your own clean energy. This comparison provides crucial information, in establishing the financial cashflow for the user from an investor's point of view.

 

Exporting Data

You can export the data in any of the charts on the Reports page in various formats.

This is especially useful for exporting a full year worth of data. Please note that if you selected High Resolution modelling, then this file is very big, and exceeds the current download limit in the Google Chrome browser - you will need to use Firefox instead.

 

Some of the Reporting Metrics Explained:

SolarPlus offers a wide range of metrics to illustrate system performance in energy and financial units, often comparing the situation before with that after the proposed system installation. This page explains the assumptions and calculation methods for these metrics.

Commercial Metrics

Cashflow Breakdown Table

This table for commercial systems gives an estimate of cashflow credits and debits broken down into categories for each year in the system lifetime.

Subsidy

The Subsidy column in the cashflow table includes STCs if applied in year one, or if LGCs are applied, these will be added in year two until the year 2030. See the LGC calculation method below.

Export Earnings

Export earnings are based on solar (and possibly storage) export multiplied by the solar-feed-in tariff set (which may differ per tariff time-of-use period). NO annual escalation rate is applied.

Tax Effective Depreciation

Depreciation defaults to the Australian simple depreciation method. The asset value is the system cost less STC/LGCs. In year one the asset is depreciated by 15% and in subsequent years by 30% with a nominal tax rate of 30%. No depreciation is applied after year 20.

Depreciation can be customised for any commercial quote on the Pricing > Financials page. You can enter the first-year value as either a percentage or a dollar amount, add a subsequent year depreciation rate and add a tax rate.

Bill Charges

The Bill Charges column shows the estimated annual electricity charges including all fees and charges (as per the annual bill comparison chart) excluding sales tax, and with the annual tariff escalation rate applied.

Cost of Finance

The Cost of Finance column will include any finance repayments including principal and interest charges.

Capital and Maintenance

The Capital and Maintenance column includes the purchase price, annual maintenance allowance and up to two reinvestment amounts for system upgrades.

Tax Debit

Commercial enterprises can expect to have income tax applied on export earnings as well as on incentives.

10. Net Cash

The Net Cash figure is the estimated total annual cost including all Cash Incoming and Cash Outgoing amounts.

11. Comparison Cost

The Comparison Cost is the estimated annual cost of electricity based on the historic consumption (or estimated load profile) and applying the tariff escalation rate annually.

12. Accumulated Savings

The Accumulated Savings figure is the Comparison Cost less the Net Cash value, providing an estimate for the total accumulated savings throughout the system lifetime for the cashflow simulation.

13. LGCs (Australia)

For information on applying LGCs, please refer to: https://solarplus.zendesk.com/hc/en-us/articles/10916024748815-Subsidies-STCs-LGCs-VEECs-ESCs-PRCs-etc#Subsidies-STCs,LGCs,VEECs,ESCs,PRCs,etc-LGCs

 

14. Carbon Emissions CO2 Reduction Calculation

The total grid energy kWh reduction is tallied over the lifetime of the system, factoring panel degradation. This is then multiplied by a carbon emissions multiplier provided for each state/territory and divided by the system lifetime in years, to arrive at an average annual value.

Solar energy that is consumed on-site and solar export are considered as reducing grid energy consumption. Potential PV production that is curtailed due to export limits is not considered in CO2e reduction calculations.

SolarPlus uses the state emissions reduction coefficient (CO2e per kWh) published by the government of the relevant territory. Where government figures are unavailable, reputable third-party sources are used.

Car emissions equivalent is based on 4.62 tonnes per year per car (Source: EPA)

Tree emissions credit is based on 0.0614 tonnes per tree per year (Source: EPA)

 

There are various report tags for CO2e emissions reduction equivalent:

  • Annual average grid avoided emissions [[carbon_reduction]] (based on solar utilised)

  • Lifetime total grid avoided emissions [[carbon_reduction_annual]] (based on solar utilised)

Values are given in tonnes (1000 gm to a tonne) so that the calculation for the carbon emissions value (either annual average or over the system lifetime) is:

Carbon emissions reduction = ‘Grid electricity use avoided’ (in kWh) * CO2 emissions reduction factor / 1000

 

15. Internal Rate of Return (IRR)

The internal rate of return is a value at which the Net Present Value (the present-day value of all future savings) is reduced to $0. That is, the Net Present Value is set to zero and we solve for the discount rate at which this happens.

Factors: Annual savings on a cash sale basis (residential sales include GST, commercial sales RoI excludes GST and may include LGCs (AU)); Optional, for commercial quotes users can select to include Depreciation on the basis set in Pricing > Financials and this will be included in all-cash basis return on investment metrics including IRR. (Proposal tag: [[system_roi_irr]] )

NOTE: PENDING RELEASE For financed systems there is a separate IRR calculation and value tag [[system_roi_irr_fin]] that can be included in proposals. In this case, the basis of the savings for each year becomes the estimated cost of grid power (escalated based on the tariff escalation rate) less the cashflow after value. Both of these lifetime costing series can be seen presented in the Finance Cashflow Table.

 

16. Net Present Value

The Net Present Value is the difference between the present value of the net cash inflows and the present value of the net cash outflows over the period of the system lifetime as determined by the user.

Net cash inflows includes: earnings on exported energy, nominal savings from avoided grid cost including the value of estimated tariff escalation rate, and nominal savings from avoided generator costs.

Net cash outflows includes: Initial purchase investment, any subsequent reinvestment in the system, maintenance costs, and supplementary grid or generator costs.

Module degradation rates (year 2 and subsequent years) are factored into all future year energy and savings analysis.

Residential vs Commercial: Annual savings on a cash sale basis (residential sales include GST, commercial sales RoI excludes GST and may include subsidies).

Optional, for commercial quotes users can select to include Depreciation on the basis set in Pricing > Financials and this will be included in all-cash basis return on investment metrics including Net Present Value.

 

17. Tax Implications and Tax Treatments

The three main areas of consideration for commercial solar finance and return on investment are:

  • Sales tax

  • Income tax

  • Depreciation

Sales tax

  • Sales tax may apply to the system price and this will be stated on the quote and invoice, although in different ways for residential and commercial customers.

  • In terms of return on investment for commercial systems, all investment factors are considered exclusive of sales tax.

  • In commercial systems, sales tax may apply to subsidies (AU: eg. STCs or LGCs).

  • For residential customers only, sales tax in terms of RoI will factor the tax in bill totals, before and after the system installation.

Income Tax

  • Any feed-in tariff is treated as assessable income and therefore a tax debit applies for any year where feed-in tariffs are considered.

  • AU: The ATO treat Renewable Energy Certificates as “assessable recoupments” and therefore subject to income tax. This may apply in the first year in the case of STCs or in subsequent years in the case of LGCs.

  • A tax debit applies for these liabilities based on the tax rate set at Pricing > ‘Financials’.

Tax-effective depreciation

  • Depreciation handling can be controlled in the Pricing > Financial page for any client-marked commercial.

  • You can set a first-year depreciation method as either a dollar value vs a percentage value and enter the value that is applicable. You can set a percentage value in the third field for the depreciation percentage in subsequent years.

  • Depreciation will be shown on the commercial detail proposals under Cashflow Table > cash incoming > tax-effective depreciation

  • Depreciation is calculated over a 20 year period

     

 

18. Estimated year 1 savings. The entire modelled electricity bill of the before scenario, minus the modelled bill of the proposed scenario.

Commercial is ex. GST and includes depreciation (if selected in Pricing > Financials).

 

 

Weather and Irradiance Data

SolarPlus sources reliable weather and irradiance data from the world leader in this field, Meteonorm, which was initiated by the Swiss Federal Office of Energy in 1985. Meteonorm has developed a global climate database based on ground measurements and satellite weather data at an 8km resolution, with over 20 years of recorded data.

State-of-the-art interpolation models combine this data to build a typical meteorological year - individual days retain the variability of actual day data, while the overall month to month is biased to reflect the average year.

Using typical meteorological year data is by far more accurate than using monthly average data, or indeed the recorded data of a specific year which, if repeated, would not be representative of the weather at that site over the system lifetime as it does not account for variations which occur from one year to the next. However, one limitation of typical meteorological year data is that while it does show multiple consecutive days of low insolation, these may not be consistent with extended rain events experienced in particular years due to La Nina or other long-cycle weather patterns. In the case of off-grid power systems, this means that the generator run-time and battery hours of autonomy calculations do not account for the absolute worst case scenario, so we encourage designers to use common sense when sizing off-grid power systems to take this into account.

 

Solar Performance Simulation

SolarPlus performs an analysis of solar power generation using a module-level simulation that generates the expected module output for any orientation at each hour of the year (8760 hours). The components of direct, diffuse and ground-reflected radiation data from the sun are derated using the Perez model, and factoring shading, glass reflectance, and soiling to arrive at the irradiance impinging on the panel front, and if a bifacial module, adjusted for on the rear surface. Adjustments for temperature and wind for each hour, and accounting for proximity to the mounting surface, provide the derating of the cell according to its manufacturers specifications.

SolarPlus features an advanced single diode cell equivalent circuit model, that is to say the cell circuit performance is simulated using the datasheet Isc, Imp, Voc & Vmp values, and using the temperature coefficients adjusted to the temperature conditions in each hourly interval in which the output is calculated. The model arrives at the five parameters used to determine the module output at the given irradiance: Light current, reverse saturation current, series resistance, shunt resistance and diode ideality factor.

According to the system electrical configuration, module and string voltages and current are modelled with allowance for the variability due to module mismatch, manufacturing tolerances, and cabling losses at each stage of the power transmission. Inverter losses due to tracker and output stage current and power limiting are calculated and inverter efficiency and AC derating factored into the usable energy potential to the site switchboard.

 

Energy and Savings Simulation

SolarPlus supports energy simulation down to 10 minute resolution in order to simulate performance of battery storage systems, consumption power flows, grid interaction and, for off-grid systems, generator runtime.

Battery system performance is modelled according to the specifications of the manufacturing and factoring roundtrip efficiency, configuration set-point limits, depth of discharge limits, and accounting for battery chemistry characteristics.

Grid interactivity levels are controlled with export limits, set-points for any battery grid charge or battery export and all energy flows accounted according to the electricity tariff structure set for the site including time-of-use, tiered tariffs and demand charge rate.

 

Lifetime Return on Investment

SolarPlus conducts an assessment of potential payback on investment factoring solar panel degradation, tariff escalation rates, reinvestment amounts in future years, maintenance costs.

More detailed return on investment analysis of lifetime savings can be generated including depreciation, costs of finance, subsidies. Discount rates are applied to estimate an Internal Rate of Return and Net Present Values of the system over the lifetime period.

 

De-rating Table

SolarPlus provides a report on the effect of the following de-rating factors, culminating in a total system efficiency calculation.

For more information, please see Derating factors

 

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