Friday, 9 July 2010

How much is enough.

How many cabin lights is enough in a narrow-boat?

I was looking through Rosie's manuals and in particular at her electrical systems last week. I wanted to start to get a reasonable understanding of her power consumption and to get to grips with her extensive set of manuals. The one thing that I did pick up on was the number and type of lights. In common with most boats Rosie has two systems. The mains or high voltage side and the battery powered low voltage side.

In general, home lighting is achieved by the use of incandescent filament or fluorescent bulbs or tubes and this process has barely changed in more than 100 years. Costs and efficiency of conventional lighting have not been questioned until recently, because most people are unaware of any alternative means of lighting. However, environmental awareness and change in attitudes have meant that new alternatives in lighting technology have been produced.

 A "normal light bulb" has a very thin tungsten filament that is housed inside a glass sphere. They typically come in sizes measured in 10, 25, 40, 60 or 100 watts. The idea is simple, electricity runs through the filament. Because the filament is so thin, it offers a good bit of electrical resistance to the electricity. It is this resistance that turns electrical energy into heat. The heat is enough to make the filament glow white hot, and the "white" part of the glow is light. The problem with light bulbs is that the heat created is wasted electricity. Heat is not light and the purpose of the light bulb is to give light. So all of the energy spent creating the heat is a waste. Incandescent light bulbs are therefore very inefficient.

As an example the wall lights in the saloon on Rosie has four 25 watt mains bulbs. Its a small saloon and 100 watts of wall lighting seems to be overkill. So I shall be looking at some alternative solutions that I can use. Solutions which can be provided by using fluorescent, halogen or the latest LED type light bulbs. The criteria being to use less mains generated power via the boats inverter or when used on a shore line. LED based household light bulbs (which are much improved) are beginning to used to replace the old incandescent and halogen lighting that you will find in most homes. I did consider replacing the bulbs with compact fluorescent light bulbs. However, low-energy light bulb replacement, using LED bulbs are a better alternative for providing an effective low power consumption lighting.

There is some confusion about how much light you get from different types of bulb and how much energy they consume. Compared to a normal incandescent bulb,  compact fluorescent will use approximately 20% of the power to generate the same amount of light. e.g. An 11 watt compact fluorescent is equivalent to a 60w light bulb.
A halogen bulb uses about 50% of the energy of a conventional bulb to generate the same amount of light. They can however become very hot
Led Replacement light fittings have advantages over standard light fittings as they produce minimal heat and use between 50% and 80% less power compared to their standard non LED counterparts. LED technology is improving all the time with new technological innovations.

This then started me thinking, should I look at converting all of Rosie's (mains 240v) lighting circuits to a low voltage operation. I could use compact fluorescent bulbs as they are more efficient and also have long life durability, better than most other bulb types. However, compact fluorescent bulbs should only be considered as the main stay for all you’re lighting needs in the home. The typical bulb size tends not to lend themselves to boats and there are only a limited number of profile types to chose from. I have a good low voltage power system available on the boat, so other methods may be cheaper and more practical to achieve.

Some of the benefits of a low voltage lighting scheme should be considered but are less well understood. Here are a list of some of the main points that I considered.
  1. 12 volts is inherently much safer for children and pets.
  2. A bigger range of good quality, smaller fittings to choose from.
  3. A better range of lamps to choose from which are brighter, whiter, more efficient and longer lasting.
  4. Some 12 volt lights are twice as efficient as their 240 volt equivalents.
  5. Low voltage systems can absorb transients such as those caused when a lamp blows and are, to a degree, tolerant of earth currents arising from a bit of damp in light fittings.
  6. DC cable losses would not be a problem in my case.
  7. LEDs only require tiny amounts of power to operate efficiently.
  8. Consider systems that could be run from solar or wind generated power.
  9. Total extended life per unit with minimal degradation of light output.
  10. Reduced cost of periodic re-lamping and maintenance.
  11. LED operating temperatures are typically 60°C rather than the 300° - 450°C operating temperatures of conventional lighting.
  12. LEDs do not produce ultraviolet light.
  13. LEDs are not subject to sudden failure, vibration or burnout as there are no filaments to burn out or break.
  14. Incandescent light sources are subject to sudden failure as there are filaments to burn out or break.
  15. Halogen bulbs are small lamps which generate considerable heat so they can only be used in light fittings designed to cope with high temperatures.

We already have a 12 volt TV, CD player, Radio and Satellite systems. Our only need to use mains power either through the Victron inverter or shore line is for a small 700 watt kettle and a 700 watt microwave. There may also be a need for a small vacuum cleaner in the sub 1000 watts range later.

Rosie has a reverse layout, the saloon is at the back, followed by the galley, then the bathroom and the bedroom is at the bow. Therefore our battery bank / inverter is located adjacent to where the majority of the power will be consumed. We only have two mains sockets installed forward of the galley. There are also two mains voltage wall lights in the bedroom area.

Rosie also has six, ten watt low voltage lights in the Saloon, four in the Galley, four in the Bathroom and four in the Bedroom. So I went through and took out half of the lights in each area except for the bathroom. It was hard to detect a significant difference in the light level. We actually preferred the apparent lower light ambiance as being a much more comfortable lighting level. Many of the lights were removed from our eye-line and made reading and watching TV much more comfortable.

We also have a galvanometer fitted which measures earth circulating currents when connected to the mains on the jetty.  A galvanometer is an instrument for detecting and measuring a flowing electric current. It produces a deflection in either direction of pointer in response to electric current flowing through its coil. I noticed at Strawberry Island that there was some small deflection on the meter which gives pre-warning of currents that can eat away at the steelwork. Most boats have sacrificial anodes fitted to protect the steelwork. However, on the jetty at Tinsley I noted that there are no circulating currents at all. So that's a plus.


1 comment:

  1. Interesting that you have two lighting systems aboard. Ours are all only 12V.

    The only 240V we have is a few sockets for when we are plugged into the shore power. We have a small kettle, electric blanket and thats about it that runs from 240V.

    All of the other systems aboard are 12V (excpet cooking which is gas) When plugged into shore power the battery charger takes over supplying the power. It seems we have quite an efficient system as we can stay in the same place for a few days with no shorepower or engine running and still be fine for power from the two 90AH batteries and that includes leaving the fridge on which is our main use of electric.


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