Page 431 - Advances in Renewable Energies and Power Technologies

404 CHAPTER 13 Photovoltaic Cooking

1.1 ENERGY AND COOKING
A heat source well above water boiling temperature is currently used for cook-
ing, classically burning flames. In developed countries, modern forms of energy
are used to make cooking fast, clean, and controllable. Mainly fossil fuels are
burned, but recently natural gas or liquefied petroleum gases (LPGs, butane,
and propane) are preferred. In the most developed countries, there is a tendency
to use electricity to produce heat, either through the Joule effect or by means of
microwave ovens or induction ranges. The energy consumption and cost of cook-
ing for an average family are generally small in comparison to heating, air con-
ditioning, and other electricity consumption by home appliances, exception made
for the low-income users [2]. This justifies consuming the more expensive option,
electricity, because of its ease of use and high availability. In the poorest situation,
such as in developing nations, and especially in the country and periurban areas,
almost only firewood is burned for cooking, either gathered directly from nature
or procured from local markets, in addition to residues from landfill or from
agriculture.
According to the International Energy Agency, about 3 billion people world-
wide depend on burning solids for cooking [3]. More than 95% of these people are
either in Sub-Saharan Africa or in developing Asia, and around 80% are in rural
areas [4]. A common first evolution from this status is shifting from firewood to
charcoal as it is lighter, more compact and inert, burns with fewer fumes, and gives
a higher and more consistent heating effect. Because of this, it is much preferred in
urban and periurban areas, although starting and stopping cooking is cumbersome
too. Conversion of wood into charcoal wastes at least two-thirds and up to nine-
tenths of the heating content in wood, needing on average 5e7kg of dry wood
for producing 1 kg of charcoal. The sustainable use of charcoal indicates that
the net CO 2 released to the atmosphere by charcoal production and end combustion
is neutral. But its manufacture is very polluting and increases user cost. It is well
known that in many places charcoal use causes deforestation, e.g., Haiti.
Using coal worsens indoor pollution and adds net CO 2 to the atmosphere. Transi-
tion to liquid fuels such as kerosene and paraffin oil reduces ash and indoor fumes
substantially but its supply tends to be irregular in many rural areas. Their cost is
high, around 5e15 times that of firewood, although the average efficiency of
paraffin cook stoves is around twice that of those using firewood or charcoal.
Bioalcohol and other liquid biofuels, such as plants oil, have not reached wide-
spread use for cooking because of high cost and complex production. Burning
LPGs is the following step forward toward safety, cooking control, and air clean-
liness. They are costly and scarce in many undeveloped areas despite government’s
tendency to sponsor LPGs for helping low-income families. Access to grid elec-
tricity is even worse in those areas and probably it will not be available in the
foreseeable future in many small and remote communities because of investment
cost. Use of electricity is very clean and controllable but its production by
burning fuels signifies emissions of pollutants to the atmosphere elsewhere.