There trigeneration is a particular field of cogeneration systems. Special is the fact that it not only produces electricity, but also refrigeration, providing chilled water down to -60 ° C, as glycol water or liquid ammonia, useful for conditioning or industrial processes. This, in trigeneration, takes place using the thermal energy recovered from the thermodynamic transformation. Therefore electricity "E" refrigeration.
Trigeneration: how it works
The process of obtaining cooling energy that takes place in the trigeneration and makes it so special compared to cogeneration, it takes place through the absorption refrigeration cycle, based on the state transformations of the refrigerant fluid in combination with an absorbent substance. For example, the water / lithium bromide pair for temperatures is up to 4 ° C, then ammonia / water down to -60 ° C.
The relationship between the cooling energy produced and the incoming thermal energy is called cycle efficiency (COP - coefficient of performance): varies from 0.7 to 1.3 and depends on the reconcentration stages of the solution, supply temperature, temperature of the refrigerated fluid and condensation. Today inlet you can have hot water from 60 ° C upwards or steam and combustion gas. In trigeneration the mechanical energy required is only that of the pumps, of the vacuum, of the solution and of the refrigerant, since the rest is the thermal energy.
Trigeneration and cogeneration
When it comes to cogeneration we mean the combined production of electricity and thermal energy through the same combustion, recovering the heat otherwise lost downstream of the process. There trigeneration it also combines these two functions with air conditioning and cooling.
Compared to the "normal" production of electricity, still a step behind the cogeneration, ours trigeneration it is able to have a higher overall yield because it exploits more energy “revenues”. In particular, it manages to waste less calorific value of the fuel, uses a higher percentage of it and this makes it appreciable and even greener. Anti-waste.
Generally in the thermoelectric power plants they convert about 1/3 of the fuel energy into electricity, the other 2/3 are lost to heat. There trigeneration it is able to exploit more than 4/5 of the same incoming energy by recovering the heat and making it a source for an absorption refrigeration cycle, just as illustrated above. In simple cogeneration, the heat is instead exploited directly, without a cycle, without the production of cooling energy. A big difference, of processes and results.
If we have a traditional air conditioner in the house, it is obvious that in terms of efficiency, comparing its COP with that of a trigeneration there is no comparison. The second loses, does not stand up to the comparison. But it is not even a comparison to make, it starts from two different assumptions. The classic air conditioner feeds on high-quality electricity, and well paid by us, while the trigeneration It provides us cooling energy only and solely by using the waste heat of another process, the one with which electricity was generated.
In the domestic context it remains feasible today especially in medium-large buildings, while it finds greater opportunities to be useful and convenient in offices, hospitals, universities or in the industrial sector, particularly in the agro-food sector, in freezing of food.
Trigeneration: systems to choose
Granted that we don't have to compare a system of trigeneration with an ad hoc air conditioner, we can still consider the idea of using one as a primary source of heat. It can work, today, because the technology is good and economically systems trigeneration they seem to be affordable. Among the various types are those with fossil fuels, those with gas and systems with biogas. Of course, to mention separately, those “Hybrids” of cogeneration and trigeneration.
When you opt for the trigeneration, perhaps conquered by this less waste of incoming energy that we talked about - a bit like when you make meatballs with the leftover Sunday roast -, it is because you have smelled the advantages of this route. The main ones are the cost reduction primary energy and also those of management, the final obtaining of a greater amount of electricity available.
In this case, the process starts from a gaseous fuel and supplies electricity, hot fluids for heating and cold fluids for cooling. The plant consists of a cogenerator to which, to have the added value of trigeneration, the absorption system must be coupled.
The gas arrives in the engine, included in the cogenerator, and there it is converted into mechanical energy then transformed into electricity by the generator while the heat recovery system converts the thermal energy that cannot be used directly. Let's see again how the gas trigeneration they have high yields because they also use the heat that should be lost.
A plant of trigeneration it can also be fed with biomass, already known in other fields such as boilers, for example: "Biomass boilers".A realized solution consists of a trigeneration consisting of two sections, one of which is fed with biomass, with consequent environmental gain.
A cogeneration section remains fueled by methane gas but the thermal section a wood chips. Thus we obtain the trigeneration, the simultaneous production, of electrical, thermal and cooling energy with a significant reduction of CO2 emissions, as well as ashes.
For the trigeneration solar we talk about a system that always produces electricity, domestic hot water and cold air but drawing "initial" energy from the sun, often capturing it with a photovoltaic panel although, with the advancement of practices and technologies, there are much more ingenious and efficient systems.
An example for everyone, it has already existed since 2010 Trinum, presented by Pierluigi Zappacosta Chairman of Innova and co-founder of Logitech, an, indeed, the first, thermodynamic system in the world with solar concentration and small size free piston Stirling engine. If the definition, so brief, tells us nothing, or little, just think that this system of trigeneration significantly reducing the footprint compared to traditional systems and is totally 100% recyclable. A feature that cannot be disliked.
In compliance with the European Directive 2009/28 / EC, Trinum also does not emit CO2, does not need an inverter, with the same direct solar radiation, it produces over 40% more electricity than a common one. photovoltaic panel. It takes up relatively little space, in case of rain, hail or strong wind, it closes in on itself.
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