Solar photovoltaic energy on farm

[Click here to download a PDF version of this information paper]

Solar photovoltaic (PV) cells convert sunlight to electricity. The size of solar PV systems can be less than one watt or many megawatts (MW). Pholtovoltaic systems have broad application in regional Australia, from providing electricity to remote applications such as electric fences to generating domestic electricity for farm houses and power for core operational processes such as the ventilation of chicken sheds.

This paper focuses on flat-panel PV, the most common application of PV technology for farm installations. Agricultural process-specific application of other solar technologies are discussed in separate papers on solar/diesel hybrid pumping systems, solar thermal drying and solar thermal hot water.

Traditionally, solar PV has incurred relatively high up-front costs. However, PV systems have long lifespans, which suits long-term businesses such as farming. Further, solar leasing options are now becoming available to property owners looking for a way to defray capital costs.[1] Rural locations and the high electricity prices paid in remote areas mean that solar PV can be an attractive investment option, particularly if the following conditions apply:

  • the current variable electricity charge is greater than 20 cents per kilowatt hour (kWh), and
  • the site has either a large roof surface facing north with good, direct sunlight or large areas of unused land close to where electricity is needed.

How does a PV system work?

Flat-panel solar PV systems can be grid-connect or standalone. The main components of both are solar panels and an inverter to convert direct current (DC) to alternating current (AC)[2] for export to the grid or on-site use, as illustrated in Figure 1. Particularly in off-grid systems, batteries and a charge

The most common solar cell technology used in ‘flat plate’ PV panels is crystalline silicon (c-Si), which represents 85 to 90 percent of the global market. In flat plate arrays, energy conversion efficiency ranges between 11 and 23 percent, with most commercial modules achieving 13 to 15 percent. A wide range of inverters is available, from units that have the sole function of inverting the electrical current, to sophisticated units that include functionality such as data monitoring and other services to ensure the inverter operates at an optimal performance level.

Solar PV diagram
Figure 1: Grid-connected solar PV system with batteries.
NSW Farmers

Particularly in off-grid systems, batteries and a charge regulator are added to provide better security of supply. Battery selection should be based on the expected electricity consumption (kWh) and the solar PV system’s maximum output. Batteries are rated for their capacity in amp hours at a given discharge rate.

In general, it is best to store electricity output from PV panels in ‘deep cycle’ type batteries, or those batteries that can discharge up to 80 percent of their stored energy without damage to the battery. Common types used are flooded lead acid, gel, and sealed valve regulated lead acid (VRLA) and absorbed glass mat (AGM) batteries.

When selecting a battery, compare:

  • the number of times a battery can be charged and discharged (i.e. its cycle rating),
  • the conditions under which batteries need to be stored,  and
  • maintenance required (e.g. often, those that do not need to have distilled water added are preferred).

If you are interested in battery storage of solar PV-generated electricity, speak with a local supplier of solar PV systems who can advise you on the appropriate type and size of battery.

Sizing your system

To determine the potential of solar PV to generate sufficient energy for your farm, you need to:

  • determine the load and load profile for electricity on your farm,
  • identify buildings or areas of your farm on which PV panels could be installed,
  • calculate the electricity generation potential of your proposed PV system,
  • estimate the savings and investment required, and
  • approach the market for quotes.

Determining load and load profile

Request half-hourly interval meter data from your electricity retailer to determine your load profile. You should aim to scale your system to meet daytime base load requirement (see Figure 2).

In the current legislative environment, it is not recommended that you ‘over-size’ your solar PV system to export electricity to the grid. Feed-in tariffs (FiTs) for solar in NSW have diminished and currently, the export of generated power is rewarded at only around $0.08/kWh, which is approximately 25 to 30 percent of the cost of buying power from the grid.

Load profiles
Figure 2: Base load and seasonal load profiles
NSW Farmers

Solar PV is not recommended as a peak load and demand charge reduction strategy. Although in some instances it may be effective in reducing your peak demand, a single cloudy day could result in your peak demand returning to the pre-solar PV profile. This will result in the same demand charges as before.

Identify buildings or areas of your farm that might be suitable for solar PV panels

Assess whether you have a sufficiently large north-facing roof surface with good, direct sunlight or unused land close to where you need electricity. As a rule of thumb, you will need 10m2 of north-facing roof/ground space for every kWp of solar PV you plan to install.

Calculate the electricity generation potential of a PV system

Use the Clean Energy Regulator’s (CER) ‘Postcode zones for solar panels’ list to determine the typical electricity-generating capacity of your location (i.e. MWhe electricity per kWp installed capacity). A typical flat plate array in NSW generates approximately 1.4 MWhe of electricity per kWp installed capacity.[1] Output is very seasonal. Summer and winter solar radiation in NSW often varies by 50 percent or more, depending on the location.[2]

The system output will also vary depending on the orientation and tilt angle[3] of the solar panels, and the presence or absence of shading and ambient temperature. In some circumstances efficiency can be increased through the use of tracking systems (one- or two-axis), which can provide an increase of approximately 10 percent in efficiency. Tracking adds significant cost, however, and generally this outweighs the benefit of increased yield.

Estimated savings and the investment required

In addition to electricity savings,[4] consider revenue from certificates under the Renewable Energy Target (RET) Scheme as a co-funding source. You can determine whether your project qualifies for Small-scale Technology Certificates (STCs) under the RET Scheme by referring to the CER website (Australian Government, 2014).

At present the up-front cost of a roof-mounted grid-connected solar array is approximately $2.30 per watt. This does not change much whether you are installing a 5 kW or a 100 kW PV system.[5] As system size increases, economies of scale do apply. However, reducing capital costs associated with equipment is typically offset by the increased up-front cost associated with planning, grid connection, network studies and project management fees for larger projects. The intersection of these factors, in addition to load requirements and space, will influence the optimal project size.

PV panels have a warranted life of 25 years. The cost of solar panels continues to trend downwards, although at a slower pace currently than in recent years. It should be kept in mind, however, that solar panels constitute less than half the cost of a grid-connected system, as illustrated below. Other variables to consider when costing out your system include: whether or not the system will be grid-connected, roof-mounted or ground-mounted; and whether storage capacity is required and if so, how much.

Solar component costs
Figure 3: Grid-connected solar PV – typical system component cost.
NSW Farmers

Off-grid solar PV system costs tend to be higher, due to additional system design elements such as batteries or other energy storage systems. If security of supply is critical, back-up diesel generators may also need to be considered.

Roof-mounted systems, although constrained by the roof surface, are often about 10 percent cheaper than ground-mounted ones due to additional installation costs (such as concrete footing and piles) for ground-mounted systems. Moreover, using roof space to generate power captures ‘dead’ space rather than consuming valuable land.

Approach the market for a quote

The installation and wiring of solar panels must be undertaken by a licensed electrical contractor or the holder of an electrical qualified supervisor certificate. You can check the license details by going to the Fair Trading website (NSW Government, n.d.) or by phoning 13 32 20. If the installed and wired solar panels need to be connected to the electricity distribution network, this work must be undertaken by a person accredited under the Accredited Service Provider Scheme (ASP). The ASP scheme is managed by Industry and Investment NSW; a list of ASPs and their contact details is published on its website (NSW Government, 2013).

If you wish to claim any state or federal government rebates, including STCs for the installation of solar panels, you should ensure the installer you use is accredited by the Clean Energy Council (CEC). A list of accredited installers is available on the CEC website www.cleanenergycouncil.org.au. Every installation carried out by an accredited installer is required to meet the Australian Standards for installation and products. The Clean Energy Council has compiled a list of approved products, including solar PV modules (panels) and grid-connect inverters.[1]

Solar visit
Figure 4: Energy auditors assessing ground-mounted solar PV near Gunnedah, NSW, during a Farm Energy Innovation Program farm visit
NSW Farmers

Worked example

Based on the assumptions listed in Table 1, the average daytime electrical load for each season can be calculated using the formula below, with the results presented in the last column of the table.

Table 1: Key assumptions.

Season

Consumption (kWh)

% of electricity use in daytime

Daytime hours
(6 am and 6 pm)

Days

Daytime electrical load (kW)

Summer

65,000

80%

12

92

47

Autumn

55,000

80%

12

91

40

Winter

80,000

80%

12

91

59

Spring

50,000

80%

12

91

37

Total

250,000

   

365

 

Based on the seasonable variability of the load, a 30 kW solar PV system is recommended (i.e. 80 percent of the spring daytime load).

Assess whether there is enough space to install this system

Then calculate the potential for electricity generation from your PV system, assuming the site is located in Zone 3 with an electricity-generating potential of 1.4 MWhe per kWp (see CER postal code list):

If the variable charges price paid for electricity is $0.25/kWh, a preliminary assessment of the financial viability of a standard grid-connected, roof-mounted solar PV installation is presented overleaf.

Table 2: Illustrative simple payback.

System capacity

Up-front cost $ (excl. incentives)

Up-front cost/W

Annual energy production (MWh)

Simple payback on standard installation without incentive

Payback with existing incentives (i.e. STC)

30 kW

$69,000

$2.30

42

6.7 years

4.7 years

Annual energy savings of $10,375 are anticipated (i.e. 41.5 MWh x $250). STCs are valued at about $680/kW or $20,400 for this system, reducing the payback period by two years. The value of STCs is typically discounted at the point of sale.

This calculation does not account for future energy price increases and assumes no financing costs. It is further assumed that 100 percent of the energy is used to displace farm energy use. A potential reduction in peak demand charges is not included, for reasons stated in the previous section.

Key parameters to include in the evaluation of quotations

In addition to installer accreditation, installation cost and warranties, you should assess:

  • the type of solar panel you’re considering,
  • the type of inverter that’s included,
  • the type of battery that you’re considering and its expected life or cycle rate (if applicable), and
  • supplier willingness to manage paperwork associated with government grants.

Further information

Solar case study, NSW - Located in Moss Vale, the Southern Regional Livestock Exchange is one of the largest saleyards in NSW. With the support of federal government funding, the Exchange installed a 30 kW ground-mounted solar PV system. The system is estimated to produce 45,000 kWh of electricity each year, while saving around 470 tonnes of CO2e.

Storage - A recent article in Solar Magazine (Australia) about developments in storage systems, ‘Going beyond batteries: storage for grid-connected systems’ has useful information.

Technical information on storage (including different battery types and their advantages and disadvantages).

Solar storage battery system types

Renewable Energy Calculator for nursery owners - The NGIA Renewable Energy Calculator has been developed to provide a simple-to-use tool for the assessment of solar and wind energy options for nursery owners. If 12 months of electricity billing data is entered, this calculator can determine the feasibility of replacing some of or a business’s entire energy requirement with a grid-connected Small Generation Unit (SGU). 

New technology: solar panel research - Stanford University (2013, November 7), Global Climate and Energy Project: Photon Enhanced Thermionic Emission (PETE) for Solar Concentrator Systems.

References

Australian Govenment, 2013. Australian Solar Energy Information System (ASEIS). [Online]

Australian Government, 2012. Installer Publications - Postcode Zones for Solar Panels. [Online]

Australian Government, 2014. About the SRES. [Online]

Clean Energy Council, 2013. Solar Accreditation. [Online]

International Energy Agency, 2013. Technology Roadmap - Photovoltaic Energy. [Online]

NORTHWEST SEED; LAST MILE ELECTRIC COOPERATIVE, 2012. PV Design Choices. [Online]

NSW Government, 2013. Electricity. [Online]

NSW Government, 2013. Solar Panels. [Online]

NSW Government, n.d. Home Building Licence Check. [Online]

Solar Choice Pty Ltd, 2012. 30kW commercial solar power installations and solar farms: Pricing, output, and returns. [Online]

Solar Choice Pty Ltd, 2013. Solar PV Price Index - September 2013. [Online]

[1] Information about equipment that meets these standards can be accessed at www.solaraccreditation.com.au/approvedproducts.

[1] The Clean Energy Regulator (CER) determined four broad zones, based on climate and solar radiation levels, within Australia. A Small Technology Certificate (STC) multiplier expressed as MWh/kW installed capacity is provided for each zone; this can be used as a general planning assumption. The ranges of postcodes and their corresponding zones can be found on the website of the CER (most of NSW falls within Zone 3).

[2] Go to the Australian Solar Energy Information System (ASEIS) (Australian Govenment, 2013) to see the variance in average solar radiation, in megajoules (MJ) per day, for your area

[3] The tilt angle of solar panels varies depending on latitude. A tilt angle of 30.2 degrees is optimal for Sydney. Solar PV suppliers will model the most appropriate tilt angle for your project; however, often this is determined by the roof pitch.

[4] It is not recommended that you include potential changes in demand charges in your payback calculation.

[5] The average price per kilowatt for a 5 kW system in Sydney, excluding government incentives, is approximately $2,300. STCs typically accounted for a discount of about $680/kW for the Zone 3 cities such as Sydney. (Retrieved on 1 October 2013 from (Solar Choice Pty Ltd, 2013)). Also see other system price estimates through (Solar Choice Pty Ltd, 2012).

[1] Sungevity (a newcomer to the Australian industry) and EnergyMatters are now offering systems for little-to-no up-front costs via roof-space lease arrangements:

[2] AC is the standard used by all commercial appliances.


This content was produced with assistance from Energetics
www.energetics.com.au

 

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