In Part 1· and Part 2 we looked at our first solar systems output and variables that effected the amount of energy solar panels produce. In this article we will explore how to use the power generated and alternate methods of setting up solar / wind powered system / systems.
Our first system was a Grid Connect system, that is the power is fed into the normal power grid. Initially it was a net metering hook up, that is we consumed the power we generated first and excess was then exported to the grid, effecting turning the power meter backwards, reducing our bill. We have now converted to gross metering, that is, all power generated is exported to the grid and we then buy all our power from the power company. While we get a larger price from the power company than we pay for the power we use this is the most attractive option. When the gross feed in tariff is less that our buy rate we will change back to net metering. The second bonus for grid connect is the low set up cost as no storage (batteries) are required. We have now loaded software PV Bean Counter·so we can share our power generation in real time at PVoutput.org·for our grid connect system.
The down side to grid connect is when the grid goes down then we produce no power, hence the implementation of a second solar system, a stand alone system.
This Stand Alone system will not attract any solar rebates as these are a one off per property, so it will have a substantially longer payback period. The initial system consisted of a single 12 Volt 120 Watt panel, a 30 Amp charge Controller, a single 130 Amp Hour deep cycle battery and a 2500/5000 Watt modified sine wave Inverter. The storage capacity of the initial system is roughly 1.5 KWH but daily production is only around 0.5 KWH from this single small solar panel. I mounted this panel on a frame allowing a more optimal angle for panel output as can be seen to the left.
The system was designed so it could be expanded by adding up to 3 more 120 Watt panels as finances permitted, plus additional deep cycle batteries to increase the storage. While seeming small at this stage it was designed with the "how do you eat an elephant?" approach, "Answer, one bite at a time". We also needed a new battery charger to top up our tractor's battery and provide extra charge for our caravans battery to run it's lights. The caravan has a smaller trickle charger solar system that is sufficient for sunny weather only. Rather than buy a mains powered battery charger I purchased a 35 Watt solar panel and a small charge controller (10 Amp). This panel was mounted on a frame that allows it to sit at a 32 degree angle, be portable, as well as being able to be mounted on the side of our shed and put power into the stand alone solar system. This is another advantage of the 12 volt system as the panels are in parallel they do not need to be of the same size or design.
We are currently investigating either a second grid connect inverter to feed excess power to the grid, or the preferred option, when the system grows sufficiently we will permanently cut over part of our power load to this system, moving us closer to being "Off the Grid".
We currently use this ·system·primarily·as a backup for when the grid goes down, though it does provide a source of low voltage lighting for our shed and power to charge power tools. During power outages, we manually cut over part of our essential load to the system. This can be a refrigerator, or our office phones / computers. During a 5·hour power outage the system ran the refrigerator with ease though it did take a substantial part of the next day to get the battery back to it's float state with only a single 120 watt panel.Note our grid connect system can be easily converted to a stand alone 48 Volt system with the addition of batteries and a 48 Volt inverter. Given the payback time of our initial system is around 3 years the grid connect inverter has already paid for itself so is not a liability.
Next step will be wind power! ·We will also look into bi directional inverters and island inverters for our final power system. We prefer not to rely on a single source of power as a single component failure such as an inverter takes the whole system down. Long term we must all take responsibility for the generation, storage and efficient use of our energy requirements.
Update
We have now added 2 x 130 Watt panels and an additional deep cycle battery to our stand alone power, or off the grid system. ·The system can now, on a full sunny day support our deep freeze off the grid. We are very close now to moving part of our power needs permanently "off the grid". The system should comfortably run our washing machine, garage door opener and the sheds lighting needs, ·as well as providing backup power for our business phone system. The panels were installed on a solid racking system with the panels angle set to maximise output in the winter months when the days are shorter. There is room for an additional 130 - 200 Watt panel, though if we opt for higher power panel (200W) we may need to upgrade the charge controller.In addition, we have also purchased a 50 Watt panel which will be installed on the top shed roof to maintain the tractor's battrey. We plan to install a 12 volt deep cycle battery and 12 volt lighting system in this shed, moving it off the grid as well. Power requirements here are minimal so it is ideal for a stand alone system.
