Cooking Electric ?

In an hybrid system you have lots of available electrical power and this leads to the idea that you should cook electric. However if your motivation is to reduce fuel use, be more efficient and lead a greener existence then electric cooking is not always the right choice. If you spend most of the time in a marina and have access to mains electricity then electric cooking is a viable option (especially if you purchase you electricity from a green supplier). If you are away from base and relying on diesel as your main source of energy then electric cooking may not be such a good idea.

To illustrate the point I compare the use of an electric cooker with a diesel cooker (see diagram below). Here I show the power delivery from the diesel fuel right through to the cooker. The energy density of diesel fuel is approximately 10.6kWh per Litre. That is to say if you burn a litre of fuel you get 10.6kW hours of energy.

An engine is typically only 33% efficient. One third of the energy in the fuel is lost in heat in the cooling system, one third is lost as heat in the exhaust gas and one third is provided as mechanical energy at the crank shaft.

Therefore the 10.6kWh in a litre of fuel produces only 3.53kWh of energy at the crank shaft. If we now follow through the rest of the electrical path we see each stage incurs further loses. A typical electrical generator may be 90% efficient. The losses incurred in charging and discharging the battery bank may be around 15% (85% efficiency). An inverter may be around 95% efficient. The entire supply chain results in only 2.57kWh of energy reaching the electrical oven for each litre of fuel burned.

If we now look at the diesel cooking option, all the energy in the fuel gets through to the oven. Ignoring any losses in the diesel cooker itself (in the same way as we ignored any losses in the electric oven) we get four times the cooking energy per litre of fuel compered with electric cooking.

So if you need a large amount of heat (as we do for cooking) and are using diesel fuel to provide it, then use an appliance that converts the fuel directly to heat (a diesel cooker).

If we consider that a cooker may require 10kW of power then to provide this electrically is very expensive. A large bank of inverters would be needed resulting in a high cost electrical system.

Using an electric oven alos requires prolonged operation of the generator with the consequential noise and increase in maintenance. Another point to consider is that if any of the high power electronics breaks down then you can at least make a cup of tea if you have a diesel cooker !

So a diesel cooker uses much less fuel, is lower cost when compared the high power electronics required for an electric cooker and the diesel option is also potentially more reliable.

In general it is best to use electric heating only when the convenience it provides out weighs any potential loss in efficiency. For example short time use of the following electrical appliances ==> Kettle, Toaster, Microwave, Hair dryer, Fan heater etc