The outside air is an energy source unlimited and always available: its use by means of a heat pump, in addition to being free, requires no no authorization process.
It appears as a source with a variable temperature: in fact, daily temperature variations occur and, in the long term, seasonal variations.
When designing a system in heat pump it is important to take account of these changes, drawing on the normalized temperature values for each geographic location: annual maximum and minimum temperature, average monthly temperatures.
La UNI 5364 associated to the main places a minimum outdoor temperature project: in areas not mentioned in the standard climatic parameters can be calculated according to altitude and exposure with respect to a reference city, according to the UNI 10349.
By virtue of temperature rises outside, the DPR 412 / 93 divided the whole country into six climate zones each of which corresponds to a different duration of the exercise period of the heating system.
In case of installation of heat pumps in existing buildings you can deduct up to 65% of the amount invested, Installation and VAT included.
So assuming a 10.000 euro expense, you will be able to avoid paying 6.500 euro taxes.
From time to time are also provided regional contributions and the application of reduced VAT rates for the works of installation is always possible in residential buildings.
I radiators terminals are most common in existing buildings and can be cast iron, aluminum or steel alloys. Their selection in the design phase is carried out according to the values declared by the manufacturers and generally work with:
The reference design parameter for determining the thermal output of the radiators is Δt (° C), ie the difference between the average temperature of water and ambient air which under design conditions is equal to 20 ° C:
The yield values are declared for Dt = 50 ° C, or for an average water temperature Tm = 70 ° C and are tabulated or obtainable even for lower values of temperature.
Performing an operation of generator replacement of an existing building, an information on the thermal requirements necessary can be obtained also by the type of radiators, the number of elements and the design temperatures.
Surface water (River, lake or reservoir) have a greater thermal instability with respect to groundwater but due to the thermal inertia of the water and their large masses, are still excellent sources for heat pump type water-water.
Il sea constitutes the heat source more widespread. In the seas around Italy the temperature varies from a minimum of 10 ° C in winter to a maximum of 25 ° C in summer: the exploitation of salty waters amplifies but the phenomena of corrosion.
Rivers and Lakes have an instability with higher temperatures, however favorable, which pass from a minimum of-4 6 ° C in winter to a maximum of 25 ° C in summer. With these waters decrease the corrosion problem but increase those of filtering because of the content of suspended material that must be intercepted before the fluid comes into contact with the heat pump.
The amount of water required for the system depends on the heat demand to be covered by the heat pump and the conditions of the source: approximately per KW of heat demand can occur from 250 l / h up to 400 l / h of water.
The exploitation of surface waters may occur in a direct way by passing through a intermediate heat exchanger the water source, or in an indirect way by exploiting a closed circuit intermediate in which circulates a heat transfer fluid.
The construction of a plant in water-water heat pumps Requires a geological analysis by a specialist in order to know the stratigraphy of the ground that houses the ground, to estimate the masses of water available and determine the direction of water flow.
Systems in water-water heat pump can be open circuit, Exploiting in a direct way the ground water, or closed circuit, With an intermediate fluidized fluid as in the classic geothermal applications.
Open circuit applications require the presence of one or more wells for water capture and its return to the ground.
The design of such wells depends not only on the geological properties of the site, but also on the water flow required to the heat pump, considering that the required flow rate for 1 KW fluctuates between 150l / h e 200l / h.