A Hybrid system that can switch between using power from Solar panels and the Grid

[Mike90250]

.... Anyone considering a good backup generator should consider batteries instead. Anyone looking at a new system today should consider they may want to add batteries in the future.

Totally a waste if you are in an area with reliable power. For 20 years, I could count the number of grid failures longer than 5 minutes, on less than 1 hand. Investing in two $5000 battery banks, that would sit mostly idle, slowly dieing till it needs replacement in 10 years (2 batteries, 10 year ea, $10,000 for 20 years) would be a horrific waste of money, when a single, $1,000 genset and transfer switch and 20 gal propane tank would have done the same job. As long as you have reliable grid. Once the grid is sick, and down for a day each month, then the expensive batteries may become a consideration.

[donald]

Totally a waste if you are in an area with reliable power. ...................

Now what if that storage earns $4 a day? $6 dollars? There's a tipping point of battery cost where the ability to load shift some solar in the home makes sense. That change will correspond with the $40,000 200 mile range electric car.

A $5000 systems that last 5 years and returns $4 a day pays for itself. We're near the point in growth where solar supplied to the grid from the home will need to be priced rationally.

[Mike90250]

Sir, if you have a load shift scheme that generates actual $ in your pocket, and can pay for the batteries it consumes, I bow to you.

Generally, the TOU schemes don't allow for any reasonable cash back at all, just a credit on the bill that resets once a year.

[donald]

The Tesla systems should easily provide these gross savings in larger homes in Hawaii. It's a big world, with all sorts of different needs and costs. Early adopters will of course be more specialized users, as well as hobbyists. But that's hardly the point. Net metering is only beneficial to encourage the initial development of solar. It has to go away.

Where I live, long power outages are always weather related. I can see a battery system that normally automatically conducts arbitrage and earns a couple dollars a day, but converts to power saving mode based on a bad short range weather forecast. My $150 home automation controller already acts on current weather, and displays the forecast.

The Tesla battery system today is designed to last about tens years with daily cycling. If they can build that on commodity batteries, so can many other companies.

[Maitland Gill]

Experimental Solar System (Update)

A Grid Assisted Uninterruptible Power Supply (UPS) that can use the power from a wall socket as it's alternative power supply.

Being able to produce our own electricity, allows us to reduce our power bill. The amount we save from this, can be used to expand our system. So the sooner we can start doing this, the faster we can become self-sufficient. Rather than wait until we can afford to install an Inverter to our Fusebox, what if we used a Grid-Assisted Uninterruptible Power Supply (UPS), that could automatically switch to using power from a wall socket (The Grid). This is for when the Solar panels don't provide enough current and require an alternative power supply.

In other words, a system that uses batteries, charged by Solar panels, to power you're device through an Inverter. When the batteries are drained to a certain level, the power supply switches to the wall socket (Grid), while the batteries are recharged again. This way, even if the Solar panels don't produce enough power to run a device, they can still help reduce you're power bill.

When you're ready to make changes to the Fusebox, the equipment that makes up a UPS could then be used in supplying power to the entire house. In Australia, the cost of replacing a switchboard is about $700. New circuits and having to rewire cables could bring this up to $5,000 [01].

This is how I think it could work:

1. A Solar panel is connected to a Charge Controller (Or Solar Controller), which supplies the correct amount of current to a Battery.

2. A Shunt is placed in between the Charge controller and the Negative terminal of the Battery.
This allows a Pentametric to measure the amount of charge coming from the Battery on the Negative side.


What is a Shunt?

[02] [03] - This is also described in Section 2: Page 13 of this manual.


The Battery, Shunt, and Charge Controller are all connected together by using 3 Lugs. This is because the Shunt, which is located on the Negative side of the circuit, requires two Lugs which are half the length of the Positive one.


What is a Lug?

A Cable Lug is an electrical fitting used to connect a cable to mechanisms. The Lug is fastened to a matching terminal or connection point using a bolt, screw or spring clip. A Cable Lug is easy to install or remove (For repairs or maintenance) and can be used when a transfer of power is required from one location to another, across multiple devices [04].


3. The Batteries Positive Terminal is connected to the Inverter, by using a single Lug. However, the Lug from the Battery's Negative Terminal, is attached to a Relay Switch first and then to the Inverter. The Pentametric can use this Relay Switch to allow or interrupt the current that flows between the Battery and Inverter. The Pentametric does this when it senses that there isn't enough charge left in the battery. For this, another 3 Lugs are needed.


What is a Relay?

A relay is an electrical switch operated by a relatively smaller electric current, which can turn on or off a much larger electric current [05]. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching [06]. They can be used in the same way as a Circuit breaker, which interrupts the current in a circuit [07].

Devices switching more than 15 amperes or in circuits rated more than a few kilowatts are usually called Contactors.
Contactors can make loud sounds when they operate, so they may be unfit for use where noise is a chief concern [08].


4. The Inverter, which converts DC to AC, is connected to an Uninterruptible Power Supply (UPS). These provide emergency power to a load when the first input fails. For this project, the battery is made into the primary source of power and the Wall Socket as it's alternative.

5. The Shunt is connected to the Pantametric, so that it can measure the State of Charge (SOC) within a battery.
The (SOC) is an indication of how much charge the Battery has left, which can be measured by observing the current [09] [10].

The Pantametric can be made to turn on the Relay, when the Battery has the same Voltage as the one predetermined by the user.

On page 24 (P30 - P31) of the "PentaMetric Main Instruction Manual" by Bogart Engineering, it is explained that the Programs P30 and P31 will allow you to enter the two set Voltages, that will turn the Relay Off and On. The Voltage that turns the Relay on, needs to be equivalent to the battery being at no more than 75% of it's total charge, least it be damaged. The Voltage that turns it off, is the same Voltage that the Battery has when fully charged. However, this will decrease over time, so it may need to be lowered.

When the Relay is switched Off, the UPS will resume using the Battery as it's primary source of power. Even if the Solar output isn't enough to support you're load, it can still help to reduce you're power bill and you won't need to worry about the batteries going flat.

This set-up only works if the cost is less than what it would be if you were to install a Grid-Tied system to you're Fusebox.

The intention of this, is to obtain Solar energy as quickly as possible. Is there any advice you could give me on what parts I may need?


Notes:

The charging source needs to provide a Voltage that's greater than the batteries, so the current can effectively flow through it [11].

This type of set-up is best used for smaller applications (Bar Fridges, Air-conditioners) so that it can take the strain off you're power bill while allowing you to gradually expand. The cost and reliability of such a system could help make Solar more accessible than before.

There are also systems called 'Plug and Play Solar Panels', which can send power back to the grid from a wall socket.
A Grid-tied Inverter shuts itself off during a blackout, so as not to harm the workers fixing the power line.
I do not know how safe these systems are during this scenario, so I cannot recommend them yet.

A Solar Regulator is a Charge Controller designed for Solar systems. The Regulator can also provide a direct connection to appliances, while continuing to recharge the battery [12].