Bespoke Power Solution – For Quarry CCTV System

by / Friday, 31 August 2018 / Published in Repair Guides, Solar Solutions




Bespoke Power Solution

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Introduction

Bespoke Power Solutions can be designed and built to suit each customers’ exact requirements. I am going to explain in detail the following hybrid system which was designed to charge a battery bank which is to power a CCTV System at a local quarry.

The Mission

After being contacted by the owners of a local quarry. We learned they had been using a small generator to power their CCTV system. However, as the generator must be located outside it was stolen one night. So, the quarry owners decided to enquire about using solar energy to power their CCTV system. They reached this decision because of two factors, 1) There would be no cost of fuel for the generator to run anymore. And 2) A Solar Power System can be secured on top of the building with the batteries and electronic equipment being located indoors.

The System Design

With any solar power system, the first thing that needs to be calculated is the energy requirement, to calculate this we do a power consumption analysis, for this project please see the table below.

The Calculation Is: Qty X Power X Run Hours / 1000 = kWh

So now we know we need 1.15 kWh Per Day with the max load being 48 Watts.

Specify Battery Capacity

The next stage of the design is to determine what battery capacity we are going to need. The energy stored in a battery is calculated by multiplying the voltage of the battery by the Ah Rating of the battery. As we know the energy and need to find the Ah needed we reverse the calculation Energy / Voltage = Ah. In our case 1150Wh / 12 = 95.83Ah. Batteries get damaged if they are fully discharged so we never discharge batteries below 50% (The high the discharge the shorter the life span of the battery will be) so we know we are going to need at least double the Ah Capacity which would bring us to 191.66Ah. This is the energy and battery capacity required for 1 day of operation. We generally need to have 3 – 5 days of back up to allow for dull or rainy days. For this project we are going to allow for 3 days of backup. So, we multiply our 191.66Ah by 3 = 575Ah.

Determine Number of Batteries

Now we need to know how many batteries this equates to. Batteries are normally 2v, 6v or 12v, we are going to use 12v batteries so System voltage of 12 volts divided by 12 equals 1 Battery of 575Ah. If you couldn’t find a 575Ah Battery, we could round it up to 600Ah and use 3 X 200Ah Batteries connected 1SX2P (One Series by Three Parallel) See the picture below (3 Parallel).

The Charging Methods

The next stage of our design is to determine which methods we are going to use to charge the battery up. For this project we decided on a hybrid charging system, hybrid means multiple sources. Which is regular battery charger and solar panels. We opted for these options as the site has a large generator which runs from time to time, so we shall utilise some of the energy from it. You may ask “why bother with solar then”, the answer is that the solar panels will generate energy most of the time, but in winter they don’t produce so much so the generator is always there as a backup. But at times the site may be closed for holidays and the generator wouldn’t be running. So, we have two sources of energy and stored energy.

The Battery Charger

Sizing up the battery charger is simple. Lead Battery charging should be charged on a 1:10 Ratio, 1 Amp Charge per 10Ah of Capacity, Approx. (Charging Li Batteries is different, but we will cover that in another post) So for our application we will need a charger of 60Amps. We have decided to go with a 40 Amp Charger as we are also going to charge with solar as well. We chose the Victron Centaur 12/40 Battery Charger.

The Solar PV Array

Sizing up the solar array and charge controller, there are two way of calculating solar panel requirements, the first way is to calculate exactly how many is need which is crucial for full off grid solar, the other way is to calculate how many can fit on the space available. In this instance we are going to use 4 X 300-Watt Panels as that’s what can fit on the roof.

The Solar Charge Controller

The charge controller, the charge controller is a device which regulates the power coming from the PV Array to the battery. Charge controllers can often work at various voltages of 12v, 24v, 36v, & 48v. There are also two kinds of charge controller PWM & MPPT. For this project we are going to use a Victron Energy MPPT 150/85 Charge Controller. We will go more into charge controllers in another post. Our chosen charge controller can regulate 1200 Watts at 12 Volts DC.

The Battery Monitor

We have also added a Victron BMV700 Battery Monitor to our system, this, via the power shunt, calculates how much energy is sent to and taken from the battery and displays the percentage of charge the battery has at any given moment.

Fuses, Distribution & Isolators

All systems should be fused for safety; hence we have added a Victron Lynx Distributor to the system, the Lynx Distributor is essentially a fused and enclosed bus bar system. Likewise, there should be Isolators connected to all inputs and outputs of a system as seen on the pictures there is a larger red handled isolator, this is for the incoming AC Power. The black handled isolator is for the DC power from the solar panels and the small red handled isolator is for the battery connection.

System Operation & Conclusion

So, to conclude this tutorial we have now gone through the entire process of designing a bespoke power solution for charging batteries from a Generator and from Solar Panels. The system charges the batteries from whatever solar is available in a day and the battery is also topped up whenever the generator is running. The system is full protected by fuses and isolators and has battery monitoring functionality as well.

If you require us to build a bespoke system tailored to your needs please don’t hesitate to get in touch, call us on 01204 558192

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