When the sun doesn't shine you need another way to cook. You can use gas or ethanol (Koko oil) but for wood or charcoal a fuel saving stove (rocket stove) is preferable.
Rocket stoves are available in different models. You can also build your own from e.g. bricks. A fuel saving stove uses the fuel more efficiently than an open fire. The temperature is higher and therefore less smoke is formed. Usually you need to use only small pieces of wood. Always consider if a fireless cooker can reduce your fuel consumption.
A fuel saving stove can be self made or bought and is often a first step to reduce your fuel cost and the first unit in your Integrated Solar Kitchen.