Stand Alone Power System (SAPS)

EcoSouth has been supplying and installing Stand Alone Power System (SAPS) since the year 2000.

These systems are used where connecting to the traditional electricity supply (ie via the poles and wires also known as 'the grid') is either not available or financially impractical. You generate electricity to power your premises independently of the grid, and you use no more electricity than what the sun can provide each day, without the batteries running flat.

Typical applications are for remote locations, (house or business). This includes situations not necessarily far from Adelaide, but where the cost of having electricity run to your property is significantly more than the cost of supplying the power you require via a SAPS

Note that all the appliances you intend to use must be listed, rated and accounted for to enable correct sizing of these components.

diagram saps

 

 

SAPS Components

A standalone power system generally contains the following components:

  • Solar panel array to produce the electricity
  • Regulator to control the charge of battery bank
  • Battery bank for storage of your electricity
  • Inverter to produce power for use by your appliances
  • Metering and switchgear for monitoring and management of your system
  • Generator for secondary power supply (optional but recommended)

Solar Array

EcoSouth can recommend the required amount of solar panels (ie solar array size) you will need depending on your load requirements.

It is important to correctly size the array to ensure you have a dependable power source year-round without needing to rely on a generator.

To maximize winter energy yields the panels would typically get installed at 45° pitch facing north. However if your roof is a facing different directions and pitches you can also get a fantastic outcome (usually by adding a couple of extra panels). If you are building you may be able to have more influence on your roof shape, which you may want to discuss with us and your builder.

The solar panels will produce a Direct Current (DC) electricity (much like a battery but higher voltage) which will be harvested by the regulator which will control the correct charge of the battery bank.

Solar Regulator

The regulator is an important component to ensure efficient power harvest along with monitoring the battery state and temperature and applying the appropriate charge profile. The DC electricity from your panels is drawn by the regulator through the DC cable from the solar panels on your roof. The regulator intimately manages the charging of your battery-bank - it bulk-charges the batteries, and is ideally suited to the final 'absorption' phase of charging, where the batteries obtain their 'finishing' charge akin to a 'trickle-charge'. 

48Vdc battery bank for solar

Batteries

The batteries are the heart of your system. They have a limited maximum lifespan, and this is affected by how well the batteries are treated; eg if they are regularly run flat, then their lifetime will be severely reduced. Based on your load profile, EcoSouth will design the appropriate battery bank type and size for your system, but it is up to you to monitor and manage power usage to avoid this.
We carefully research manufacturers and suppliers of solar batteries, and we find there are really not many brands that can perform correctly in a typical storage shed environment in SA! The brands we have used do achieve their forecast life of 8 to 10 years when properly looked after.
New battery technology is starting to appear, and again we will take our time to carefully choose brands and models that we believe will perform and last the distance.
The batteries of course supply power overnight, and this is where they typically have the regular deepest discharge, and this makes up the daily 'Depth of Discharge' (DoD) deep-cycling that the batteries are designed to achieve.

Inverter

The inverter produces 230V AC electricity from the DC electricity in the batteries on an 'as needed' basis for all of your appliances. This is a BIG ask for an inverter! Only properly designed ones survive! The typical appliances found in households and commercial enterprises are not kind to the power electronics inside inverters, and the type and size of inverter must be planned and selected carefully to avoid outages due to overloading of the inverter. The solar stand-alone inverter is ideally required to last for two decades or more - we believe proven experience in this field is crucial for making systems last the test of time.

Metering and Switchgear

An electricity meter is installed on your premises to monitor your electricity usage. Why - isn't your solar electricity now 'free'? Yes, but this kiloWatthour (kWh) meter is now your friend. It tallies all the power you are using over time. This can then be compared to the power you are 'harvesting' from the solar array. It is a 'budgetary' process - if you 'overdraw' your 'account', ie use more power than you harvest; then your batteries will go flat, with subsequent reduction of service life depending on how many time they go flat per year.

The 'switchgear' is the remainder of the wiring, isolators, fusing, etc, used in the 'equipment room'. These parts are CRUCIAL in their selection and configuration. Get this wrong and you may have problems ranging from poor charging, inverter drop-outs, overheating, and overall poor performance and shorter service-life.

Generators

Generators are recommended as they can be beneficial for backup use, eg if part of the system fails or requires servicing for whatever reason.

Generators are required if you want to run appliances that have large instantanous loads, such as welders or if you are using more power than usual for say an event or party.

If the system is sized correctly, and no new appliances are added, then regular use of the gen-set in winter can be avoided.

Fixed gen-sets and high-current battery chargers can be added as part of installation or a later date if circumstances change. 

Important General Considerations

Building? If so, you have an *incredible* opportunity to make your life easier, through good selection of design and materials! Please contact us for discussion and more details. Do not build 'cut-price everything' as you will 'pay' in terms of inadequate heating and cooling, which means uncomfortable living for you and your family.

  • If building it is generally best to start planning appliances and SAPS early to reduce run-away costs
  • Panels typically are mounted on either a long shed, or house roof. 45° pitch north facing roof is typically most appropriate for matching to winter load requirements.
  • Batteries and equipment should be installed in a location that stays relatively cool and requires about 3-4 square meters. This may be a purpose built insulated enclosure
  • Battery life may only be 8-10 years (even less if not cared for) before requiring replacement. Cost of the replacement will be dependent on the size of the battery bank required.
  • System is sized to provide enough power throughout the year, the most critical months for most systems is May, June, July, with the rest of the year generally having more than enough power
  • Careful selection of appliances and lighting must be made to avoid runaway costs (ie energy efficiency is very important!)

Appliance and Load Considerations

  • Most typical household appliances may be run eg kettles, vacuums, microwave, fridges, washing machines, dishwashers, computers etc
  • The number, size and timing of use of appliances will determine the size inverter you require (ie peak load)
  • The usage (run times) of appliances will determines the size of the solar panel array and battery bank required
  • Night time usage patterns is a significant factor for determining battery bank size needed
  • Don't forget your appliances and tools in your shed/workshop as part of your load requirements
  • Appliances with large instantenous loads (ie welders) should not be powered from the SAPS. These should be powered from an appropriate generator.

Cooking - usually obtained via gas-bottles, but also possibly: use of a microwave oven, or use of combustion heater with hob and small oven compartment. Note that heating elements in ovens and stove-tops use *exceptional* amounts of power, and will increase your system sizing!

Hot Water - usually obtained via gas-bottles or solar hot-water panels, but could use 'wet-back' combustion heater, ie water is heated in copper coils at the back of the combustion heater, and cycles into a hot-water tank. Note that water heating using electric elements consumes larges amounts of power and will increase your system sizing.

Sewage - most locations where SAPS go don't have access to the mains common effulent disposal system, so you will be needing a system to manage this wastewater on-site. Some systems use little to no electricity, whereas others may have large electicity usage requirements. Do assess the options that are put to you so you can reduce the power use and hence reduce the cost of the SAPS. 

Heating / Cooling - heating using the SAPS is not recommended, as winter is typically the lowest energy production periods. Combustion or gas heaters would be recommended for heating. In summer ceiling fans can provide a level of comfort without large power requirements, also a small air-conditioner (eg 1kW power input) could be factored into your load profile. Reducing heat gain in summer and heat loss in winter through effective insulation and/or treatments to doors and windows provides comfort without creating additional SAPS cost.

Pressure-pump - if you do not have access to mains water, you will need to be self-sufficient for water (ie rain and/or bore water combinations). You will need a pressure-pump for your water supply, which is a critically sized item. Most homes should not need more than 550W input power (equates to 450W output), but a larger than standard pressure tank to reduce the number of start-times is beneficial (as more power is used when starting)

Swimming pools / Spas - consume quite significant amounts of power (large water pumps, chlorination equipment etc). These will significantly increase the amount of solar capacity and even battery capacity required

 

Wind Generator

 

This is a short overview, and it will raise more questions than answers. Please contact EcoSouth Solar and we would be happy to discuss your unique needs for Stand-Alone Power.

We are happy to quote for your solar power system

Please contact us on 8371 5655