We jotted down everything that we thought would require power, even if it sounded silly
and then went through a process of illumination, coming up with a ‘U-beaut-wish-list’. We say ‘wish-list’ as this is normally well
over the top and some severe culling was required.
The electrical items were then placed into AC and DC power requirement sections.
In our example it calculated that one needed 111 Ahrs (excluding the desalinator) or 151 Ahrs (including a small 12Vdc electric type desalinator) to cover the type of set-up we needed for each day (or 24 hour period). And yes, this figure is relatively high when compared to others. We say, “our boat not yours”.
A clear understanding of Basic Electrical Jargon has saved many hours of frustration in problem-fixing.
One of these understandings was the vessel power voltage of 12V DC over 24V DC, as many more appliances and components are available that utilise 12V, lowering building our costs.
This allowed us to fit into the Australian Standard AS3000 - Section 7 (in particular
7.5-6-7-9 & 7.14), which refers to the design rules that pertain to “Very Low Voltage Systems", being 12V DC.
The most common forms of power generation on yachts include solar panels, generator/s (separate portable generator units), alternators (units
making power from available and/or separate motors, usually the motors powering the boat), wind generators and water generators.
We will utilise solar panels and a portable generator/alternator.
Why is it that one cannot locate a generic electrical system/diagram that can be used for their own electrical system on a boat? A similar I suppose would be like asking a butcher ‘how to plan Christmas day’. He will supply the meat and sausages, but would have no idea on presents, ovens or even who to invite.
Each boat is different
and all setups are different and require different needs.
To calculate the initial electrical budget we jotted down all the components (including wiring) and tried to get an accurate honest figure. We then bit our tongue and squirmed at the power required.
AnElectrical Matrix allowed us to quickly change and modify (or more correctly – teach us) how to conserve energy and make best use
of the power. More importantly, the Electrical Matrix gave us the power required to meet our newly planned energy budget.
For the purists in ‘electrical-know-how’, this may not be for you as there are phrases and words used which may
not be strictly correct in the ‘purists eyes’. We strongly recommend that a qualified electrician be used in the connection of your
vessels appliances.
‘Green power’ is climbing up the priority ladder to such an extent nowdays that some predictions of fossil fuel costs (scorned at 10 years ago), are coming home to roost.
We have chosen to be proactive and endeavour to be as reliant
as possible on solar power as we possibly can. PureMajek will carry a few more items such as additional solar panels and batteries
which will surprise some and be talked down by others.
PureMajeks electrical system has Solar Panels developing sufficient energy to charge three of the four Batteries to provide 12Vdc power to the vessel.
The best we can achieve is based on ‘calculated risk’, with a system of replenishing energy (electricity) given proven techniques of small vessel power generation. A genuine decision had to be made on what we were going to use the boat for as this dictated the requirements.
Puremajeks
panels are wired in parallel (given the manuafacturer specification requirement) then run via two 25.7 mm2 copper conductor cables
(one positive and one negative), reducing the cable numbers in the turret cavity from eight to just two, down 8.5m to the battery
via the Smart Charger (controller).
They say that Voltage Drop should not exceed 2% in a good 12Vdc system. Using the Australian AS3000 calculator, the expected Voltage Drop in our case will not exceed 1% (or 0.1V from 17.7Vmp), see the ‘CD’ for expanded information.
Puremajek will be using four panels as opposed to one very large or even two large panels. The reasons here are:
Ø Ourpower requirements,
Ø Redundancy, and importantly
Ø Allowing
the larger spread of panels over the surface, reducing the 'shadow effect' caused by sails, masts and even sun position.
Most
solar cells are made up of silicon which becomes the conductor in the cell. To this, other semiconductor layers are added. Small amounts
of electric current are then extracted from the cell once day-light excites their electric field. Silicon cells are commonly made-up
under the headings of monocrystalline, polycrystalline and amorphous. Also included now days on most panels are Blocking Diodes and Bypass
Diodes and they have two totally different jobs to do.
It needs to be remembered that the manufacturer panel specifications are there either as a regulatory requirement and display optimum qualities of the product or there to cover litigation issues. The implications of this are enourmous, as the true figures for those days where temperatures above 250C have to be addressed by you and I.
Careful assessment of the efficiency of a solar panel and
contributing power generation factors should soon ring a bell. Having said this, we planned worst case when sizing components such
as the cabling and Smart Charger. There are unusual factors such as cloud-edge-effect that can momentarily spike the generation system
every now and then, and these worst case buffers need to be built in.
The panels we chose to use were 90W. For the more adventurous,
their statistics include:
Ø Cells are monocrystalline silicon solar cells and are covered with
tempered glass,
Ø SunPower SPR - 90
Ø The solar cell efficiency at 16.5% which we believe to be reasonably efficient when compared to other similar brands,
Ø Rated voltage is 17.7V (Vmp),
Ø Rated current is 5.1A (Imp),
Ø Open Circuit Voltage is 21.2V (Voc) , (The maximum possible voltage across a photovoltaic cell; the voltage across the cell in sunlight
when no current is flowing), and
Ø Short Circuit Amperage is 5.5A (Isc) – (The current flowing
freely through an external circuit that has no load or resistance; the maximum current possible).
Understanding the specifications can be a little tricky.
