Soft vs Hard Energy

Energy is often divided into two types: renewable and non-renewable, these are said to come from “soft” and “hard” energy sources.

As we worked to make Maringret less dependent on land-based systems we conducted research into energy as that is one of the three large intakes on a boat (along with foodstuffs and maintenance & repair supplies). Our research brought us to energy types and techniques which we have tried to list and summarise here.

One thing we had learned from years on a boat was that “silent is beautiful” as far as power generation goes. Almost all modern boats incorporate electrical circuits, for safety reasons if nothing else. We have come across engineless wooden boats but even they had some electrical for such things as lighting or radio or a navigational instrument. The need for an electrical supply seems to be virtually universal in boating although there is a large range of usage from negligible to permanently operating generators. There are a number of methods to generate the power:

  • shore power
  • auxiliary engine (including gensets)
  • solar panels (see our page here)
  • wind generator (see our page here)
  • towed log (generation by towing through the water)

These may be classified into hard and soft energy sources – also referred to as renewable or non-renewable. Soft (renewable) energy sources are typically the sun and wind or tides (e.g. towed log) and they typically have an outlay cost but no ongoing expenditure. A soft energy source typically is free of charge and continuous in supply whether it is taken advantage of or not. Soft energy paths tend to be silent or very quiet. Hard energy sources consume some substance such as petroleum, wood, coal and the cost of the fuel (and other consumables such as service items and lubricating oil) is the cost of their operation. As most hard sources involve internal combustion engines they tend not to be silent. Shore power can be either hard or soft although most times it will be from hard energy sources.

The use of soft and hard energies is a topic of almost philosophical content, for those interested there is a book Soft Energy Paths by Amory B. Lovins. The book is from the 70s (although there may be an updated edition) and deals with the choices between the two energy groups and some of the implications. Lovins’ discussion from the 70s anticipates events which did not occur until the new millennium and are still unfolding. Another book that takes these events and projects them into the (not too distant) future is The Long Emergency by James Howard Kuntsler. These books may seem far removed from the configuration of a sailboat electrical system but are certainly interesting background reading on a topic that, although mainly dealt with by boaters and owners of RVs, will soon become mainstream conversation for society as a whole. Energy decisions on a boat are simply the same question but asked and answered in a smaller environment.

Within the energy sources typically found on a yacht disconnected from shore power there is a magnitude of range in capacity, below are the figures from Maringret:

auxiliary engine (50A alternator) 650
solar panels 300
wind generator 200
towed log 90 (this is based on friends’ figures as we do not have one)
Note: a voltage of 13 volts is assumed for wattage calculations in this article

The power available from the engine is about 7 times that from a towed log but the cost of operation is vastly different. When massive power is required there is no alternative to an auxiliary engine, but with consideration, many things can be achieved without it by planning and having dedicated battery capacity available. The complicating factor is that certain conditions are necessary for the soft energy sources to work: there must be wind or sun or water passing under the hull. One untouchable factor for the auxiliary diesel is that assuming the mechanical aspects are in order, it offers power on demand. An overcast, windless day at anchor will yield nothing from the soft energy paths but the auxiliary engine will still provide power until it runs out of fuel.

The flip side to the auxiliary engine is the cost of operation: fuel, service items such as oil, filters, belts, wear and tear on what is an expensive piece of machinery with a finite lifetime. Conversely the soft energy paths are more of a fixed cost for their lifetime. Our solar panels are still operating as efficiently as they did 10 years ago when we purchased them, of course if they were to break then they will have to be replaced.

As mentioned above, soft energy systems are dependent on the wind or sun or water flow – if there is no source then there can be no energy capture. If the battery banks are viewed as “energy reservoirs” then a corollary becomes evident which is:  once the batteries are fully charged, no additional energy can be secured and stored. The implication is that the bigger the “energy reservoir” the more energy can be captured for later use. This means increasing the size of the domestic battery bank is one way to increase energy independence. Another page covers sizing your battery bank(s) (click here).

One lesson we have learned is that most people selling batteries do not know a lot about batteries. Even if you go to the large battery dealers they will “talk up” what they have to sell. The best advice we found was in the Cruisers Forum where there were some people writing up multi-year tests they had made with different types and makes of batteries.

Maringret came to us with gel cell batteries and they functioned flawlessly – they were performing well when we replaced them. We replaced them as we did not know their age and wanted to replace them before they failed. Our second generation of gel cells is performing equally well. The batteries have been treated very badly on occasion such as when the alternator stopped charging on a 24 hour passage and one battery ran the electric fuel pump for the whole time. Unsurprisingly it could not turn the engine over once we stopped the engine but after recharging it was indistinguishable from the other batteries.

With soft energy, the appropriateness of one type of power generation depends so much on location. When Maringret was in the North and Baltic Seas there was a wind most days which generated a lot of power for us. Where as in the Mediterranean where the winds are more intermittent than steady, we depend on solar power. Our Air Breeze wind generator has now been down for over 3 years. We can not find a repair facility for and the manufacturer seems to have gone out of business. But as we are in the Mediterranean where winds are intermittent but the sun shines for a long period every day we decided the best thing was to double our solar capacity (from 150W to 300W). That cost us less than what the freight charges would be to return the wind generator to a repair depot in Europe. However, were we still in more northerly climes, with limited solar exposure through cloud cover, lower angle above the horizon and shorter season, we would have prioritised repairing the wind generator and probably not doubled our solar panels.

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