Solar & off-grid Tech

 

Solar installs & Off-Grid Tech

 

Adding a single or series of solar panels;  

is a great future investment and method of generating free electricity;

Which has a multitude of uses from maintaining battery level while in storage prolonging battery life by reducing unnecessary cycles powering 12 Volt appliances charging power banks or mobile devices even assisting with heating up some water for use in the taps,

There are currently two Types of solar panel available on the market Solid/Rigid panels which typically have a 25-40MM aluminium frame,

And flexible panels which are typically 2-6mm and can be mounted on curved spaces

Delving slightly deeper into the dynamics of both types of panels and beginning with solid/rigid panels

The most Basic form of a solid solar panel is a polycrystalline,

Polycrystalline Solar Panels

These panels have a distinctive blue tint on appearance

The manufacturing process consists of many silicon fragments;

These fragments are melted together to form photovoltaic (PV) cells

The PV cells absorb UV rays from direct sunlight causing the electron cells to become stimulated and It is the movement of these electron cells which generates an electrical current,

The generated current is then captured by tiny conductive bars within the structure known as fingers, The fingers must be thin in order to allow as much light as possible pass on to the solar cells where the current is generated,

If you can imagine these fingers as being a series of back roads within a country; these fingers then feed current to a motorway known as the Bus bar, 

The bus bar is a thicker conductive metal strip which can allow for a greater volume of current to flow simultaneously, the bus bars are linked in series and transfer all of the collected current to the cable outputs of the panel.

The polycrystalline panels require direct sunlight to operate most efficiently

They are not so good under cloudy conditions,

the entire panel will also stop if partially shaded by a TV aerial, a leaf or tree branch Polycrystalline panels are generally 13-16% efficient,

Efficiency

13-16% Efficient; 

how is that figure calculated & what would 100% look like?

Well solar panels are far from perfect at converting light into electricity; the best one can do at the moment is 40% maximum efficiency,

The efficiency percentage is calculated based on the amount of light which the panel is capable of using to generate electricity, some types of panels do this better than others And I’ll discuss that briefly going forward;

Now that we understand the basic structure of a solar panel and how it operates let’s move on to a more efficient variation of solar panels which are; Monocrystalline

This type of solar panel; are generally more expensive; and this is partially due to the more refined manufacturing process

The mono crystalline panel is made from a single crystal silicon structure (P-type silicon)

Which allows the electron cells to move more freely without any impurities within the structure This high purity structure not only makes them 15-23% efficient it also makes the output consistent at high temperatures

The mono crystalline panels are more aesthetically pleasing as they are piano black on appearance as opposed to the Navy Snowflake appearance of the polycrystalline

A slightly more advanced variation is the N type mono crystalline solar panel

The N type is doped with phosphorus instead of boron which creates an excess of those electrons increasing the effects of how the panel generates electricity under direct sun as well as during cloudy conditions

They also have an anti-reflective coating which masks the silver bus bars on appearance

The number of bus bars has also been increased to reduce resistance providing 40% greater output within the equivalent size of a polycrystalline panel

In other words, you can obtain a 120W N-type monocrystalline panel and fit it in the same space as an 80W polycrystalline with the added benefits mentioned above.

Progressing on from N type mono crystalline

a well-known company; Renogy are currently leading the scene with their Shadow Flux N Type Monocrystalline solar panels which have split bypass cells

allowing them to bypass any section of the panel which may become shaded or covered by Leaf’s or an aerial mast where any other solar panel would have essentially ceased operation under such conditions making them ideal for caravan or Boat use.

Domestic & Mobile Solar Panels Is there a difference

The only difference between a rigid solar panel which is sold for domestic use and those marketed towards the mobile & Marine; is there overall size, the three to four variations of solar panels detailed above; are the same variations available for domestic & mobile use.

Panels designed for domestic use are generally cheaper than the top branded & highly marketed mobile variations,

So, if you have the space to fit a domestic panel on your mobile unit, there’s a level of cost savings to be gained in that aspect of the build.

Flexible Solar Panels

There are four types of flexible solar panel structures with three of those variations currently available on the market

The common ground among 3 out of 4 of those variations to date is less efficiency than the most basic rigid polycrystalline solar panels

Aside from that factor they are prone to overheating due to lack of airflow beneath, they tend to be more expensive than rigid’s and have a 25% lower lifespan

Some of these factors are said to change in the next 3-5 Years where the efficiency of flexible solar will be equivalent to that of today’s rigid N type monocrystalline in around 30% efficiency

However,

for the moment the flexible solar panel; is very much in a development stage with a lot of improvement among the horizon

At present; I would prefer to fit a rigid polycrystalline at 15 to 17% efficiency rather than flexible unless there is no option for the alternative applications such as the discrete van camper teardrop camper kayak or anywhere there’s additional weight would be an issue

Thin film flexible solar panels (efficiency 7-14%)

This variation is generally an aluminium or fabric base which have photovoltaic materials the fabric-based variation is highly portable however least durable for long term use

Organic flexible solar panels   (efficiency 14-17%)

This variation is primarily made of organic material with graphene electrodes to assist performance they are thin flexible and lightweight.

Silicon crystalline flexible solar panels (efficiency 17-24%)

This variation as the name suggests a silicon based which assists the output they are flexible up to a limit of 30-degree bend,

Pero Skite (PSC) flexible solar panels (efficiency 29-35%)

Hybrid of organic and inorganic lead or tin halide-based compounds such as methyl ammonium lead halides the unique crystal structure of Pero Skite allows for efficient light absorption and is capable of being applied to a surface less than 0.5mm thick

 

Solar panel wiring series or parallel

When installing two or more solar panels to a single array;

There can be many combinations to the wiring configuration of solar arrays,

It is possible to fit mismatched sizes such as a 100w & two 200W

However, for the purpose of this general discussion; effectively you are creating one custom shaped & sized solar panel/array.

Wiring in series (Voltage adds up while the Amps stay the same,

This is where the positive from one panel links in to the negative of the next panel daisy chain

Simple, cheap if one panel is shaded or damaged this has a knock-on effect to the overall output of the entire array

Wiring in parallel 
(voltage & Amps increase)      

Combine all positive and separately combine all negative, it is important in this configuration that each panel has its own MC4 in-line fuse.

More cables involved, branch joiners, thicker cable,

If one panel is shaded or damaged, it has less impact on the overall output of the array as in mild cases; it only affects that specific panel & the inline fuses prevent the load from the rest of array from feeding to the damaged panel instead of the battery & potentially setting that damaged panel alight.

Wiring in series parallel 

(voltage increases & Amps double)

Two sets of two solar panels first wired to pairs in series followed by then being wired in parallel before feeding to the solar breaker,

This method increases the amps however if one array becomes damaged it will carry a greater impact to the overall output of the array compared to wiring each panel in parallel as they are in series prior to being wired in to a parallel array.

Each of these wiring configurations can help you to get the maximum value from your solar charge controller as well as the maximum efficiency output from the solar array.

Solar array efficiency

Yes,

following on from discussing the efficiency of the solar panel itself; depending on the number of panels you add together and their sizes; can have an impact on the overall efficiency of the specific solar array; too many panels on an array can result in the last panel providing zero benefit or contribution.

So, if planning to form a solar array; the overall efficiency of the planned layout is something I would recommend researching prior to purchasing all of the panels,

Personally, in my own array; I’ve got 3 x 200w Panels and 1 x 120W panel

If I was to wire all of these in parallel; the 120w panel would reduce the efficiency of the entire array; I wanted to keep the weight down to wiring in series wasn’t an option that I was willing to carry out, as result; I’ve installed the 3x 200W panels to one series feeding to a solar charge controller & the 120w panel to its own separate solar charge controller.

 

Solar Breakers

With all options of solar panels addressed as well as a brief discussion on wiring configuration;

now moving on to the next component the solar breaker;

which is essentially a circuit breaker the specifically designed for DC loads to be used between the solar panel/panels and the solar charge controller,

Solar breakers are available in a range of rated sizes to best match the peak output from the panels of your specific setup & the breaker should exceed the maximum voltage of your array in order to be strong enough to confidently break the circuit.

Ideally not switching on/off while the panels are under load from the sun.

 

Solar Charge Controller’s

The DC power from your solar panel/array cannot be sent directly to the battery;

we must use a specific type of inverter also known as the solar Charge controller

Solar charge controllers come in various sizes to closely match the maximum level of power which the solar panel is capable of putting out

There are currently two variations of solar charge controllers available on the market in a wide variety of sizes to match the output of raw DC power from your solar panel/panels,

Solar panels are like a fishing net to catch the rays

The Solar charge controller is like the harvester; takes in fluctuating raw power from the solar array & puts out consistent pulses to charge the battery bank

Solar Charge Controller efficiency is determined by how good the solar charge controller is at processing the raw power feeding from the solar panel/panels and reducing it to a voltage and amperage which is acceptable for the battery to receive,

To summarise so far then; the solar panel efficiency is how good it captures the light & turns it to DC power, the array efficiency is how well matched the solar panels have been configured and now the solar charge controller efficiency; is how good it is at receiving that Captured DC power and feeds it to your battery or battery bank with minimal loss or transition to heat.

The solar charge controller is powered from the battery; much like a dividend in a volume of shares; it receives a percentage of return on its investments which assists its operation to further feed the bank.

The first variation: 

PWM solar charge controller (Pulse Width modulation) (65-69% efficiency)

The device itself consists of a Power supply, Pulse width modulator, Sensing and controlling circuitry, Load switch& a display HMI (Human-Machine Interface) display,

This technology regulates the voltage from solar panels to batteries by adjusting the width of the pulses sent to the battery. 

It effectively reduces the voltage to match the battery's voltage, 

which can lead to energy loss when the panel voltage exceeds the battery voltage 

PWM controllers are simpler, less expensive, and best suited for small-scale applications where the solar panel and battery voltages match. 

PWM controllers are less expensive, and best suited for small-scale applications 20-200w solar on a 12-24V system where the solar panel and battery voltages match. 

 

MPPT solar charge controller (Maximum Power Point Tracking) (95-99% Efficiency)

A more advanced solar charge controller is an MPPT; these units continuously monitor the output of the solar panel/array to find the optimal operating point,

They convert the excess energy in to additional current which then increases the level of amps;

maximising the capture & harvesting of the energy,

What is current/amps

Current is a term commonly associated with the sea or a flowing stream,

Well much like a stream the current in electricity is the rate of flow of electrons in columns per second within the cable; Which for electricity it is measured in amperes

One Column per second equals one Ampere of current, two Columns per second equals two Appears of current and so on.

These MPPT devices are more expensive than PWM due to there more complex design, however they are a better investment as they provide a 30% greater output in comparison to the cheaper alternative,

MPPT Solar Charge Controller is the latest technology to date;

The most reliable brand of these MPPT solar charge controllers in my opinion would be from Victron Energy.

 

To summarise a basic system in my opinion the best system for maintaining your battery in today’s market;

would be the combination of a Renogy Shadow flux 120W N-type mono crystalline solar panel 

& a Victron-energy Smart Solar 75-15 MPPT controller

Solar Circuit Breaker

10 Metre Solar Cables

Solar Panel Mounting Kit & Cable Grommet

To further complement this setup and optimise battery lifespan; 

I would recommend adding a Victron Energy smart-sense battery monitor,

This Smart-sense battery monitor attaches to the positive & negative terminals of the battery, it then sticks to the side or the top of the battery,

It then continuously monitors the battery voltage & temperature 

The device can not only display a 30-day rolling log of battery voltage and battery temperature via the mobile app on your phone,

This Smart-sense device will also independently communicate with the Victron Energy Blue Smart MPPT controller wirelessly via Bluetooth.

Where it is capable of continuously controlling the rate of charge from the solar to the battery Depending on the battery voltage and the battery temperature,

This additional smart device is capable of shutting down the solar system should a fault arise with the battery or the temperature is at a level which would be unacceptable to charge the specific battery type.

Based on the configured charge profile set on the Victron Smart MPPT Controller.

To Be Continued