Energy is an essential element in all productive processes. In both the
agricultural and transformation industries, however, its irreplaceable
importance is often underrated.
Indeed, in richer countries it may be observed that energy:
does not pose important technical problems.
On the other hand, energy becomes a priority when one of these conditions no longer holds, which is the typical situation in developing countries.
The question of energy supply and the choice of related technologies is
generally tackled using quite different criteria, depending on the
existence or absence of grids for the continuous supply of energy (e.g.,
electric grid, methane pipelines, etc.).
In the latter case, the main problem concerns the technical aspects
connected with energy self-sufficiency (i.e., essential requirements will
have to be met even at high costs).
In the former case, however, the following factors are determinant:
the risks connected with individual energy production.
In addition, situations which fall somewhere between these two extremes also exist. An example which is particularly common in some countries is connection to the electric grid, with simultaneous individual production of thermal energy. The user is always willing to evaluate various plant designs for the latter type of energy, and his final choice is not always the most economical or rational plant (indeed, expensive features, such as increased functional reliability, may be considered useful).
In summary, when connection to a grid is possible, the supply of energy is usually based on strictly economical considerations, while in other cases a wide range of situations may exist, which have to be examined on a case by case basis.
This fact is extremely important when it comes to selecting energy conversion technologies.
In all cases, the supply and production of energy pose two types of problems:
choice of the most suitable source and energy plants (in case of absence or complete reconstruction of the plants themselves).
Existing plants are frequently the basis for operation.
This is the case when productive activities have been functioning for some time, and all of their technical aspects have been resolved (though perhaps temporarily or improperly).
In this context, the various energy plants could be re-examined for any one of the following reasons:
the negative influence of these plants on actual processing or the quantity of product obtained (e.g., a boiler which is too small to guarantee a consistent level of pasteurization).
Experience has shown that:
in case c), solution of the problem may require repair of a plant malfunction or, once again, a new plant.
In all three cases, before formulating a work hypothesis, it is good practice to determine:
requirements (which, as noted in section 3, are proportional to the quantities of milk processed or transformed), broken down by type of energy (electric energy, low temperature thermal energy, etc.).
The next step is to determine whether consumption levels and requirements are compatible (i.e., acceptable) in terms of:
environmental impact (generally based on the use of biomass or the elimination of refluents of some types of energy transformations).
The proposed method of analysis can lead to two results:
the existing plant requires radical alteration. In this case, the situation is similar to the one described in section 2.3.
Both renewable and conventional energy sources may be considered in the various hypotheses. At this point, two questions must be asked:
which of the available renewable sources should be preferred?
Logically, choices a) and b) should be made solely on the basis of economic
criteria.
In other words, the most suitable source is the one that is the most
advantageous and attractive from an economic standpoint. At most, a
decision has to be made about whether the analysis should involve
individual plants (microeconomic analysis in which the number of variables
is generally limited) or entire regions or nations (macroeconomic analysis
in which the number of variables is usually quite high).
When drawing up a list of the various energy sources to be considered in a technical-economic analysis, the following aspects should be included:
available renewable sources. These sources should be determined by an analysis of the pedologic and climatic conditions of the site under examination (generally, they are connected with the presence of rivers, windiness, solar radiation, etc.). Since milk processing normally continues throughout the year, sources whose energy intensity remains fairly constant in every season should be preferred.
Once the most suitable sources have been chosen, the right technologies for
energy conversion must be selected. As mentioned above, this phase is
influenced by the presence or absence of grids for the continuous supply of
energy.
In the latter case, reduction, when possible, of the peaks of energy demand
is especially important. This will limit the size of the generators and
increase their use.
At this point it may be necessary to examine the possibility of carrying
out rationalization operations aimed at increasing the compatibility of
requirements and available energy. These operations may involve the
adoption of energy-saving technologies (e.g., heat recovery from
refrigeration, to be used for the production of sanitary hot water) or the
drawing up of special time-tables for cheese production.
The choice of conversion technologies is mainly influenced by:
the possibility of modifying milk processing or conservation plants in order to facilitate the introduction of a given source (as emphasized in section 3.1).
In an attempt to provide objective data for evaluation, section 4 will discuss individual sources, and sections 5 and 6 will review various energy conversion technologies.
