SOLAR SYSTEM FOR COMBINED SPACE HEATING AND HOT WATER

Ziel

This project comprises the installation of a solar energy system for the production of heat during the winter months, summer cooling and the preparation of hot water for the textile machinery research centre, Pordenone. Expected energy production amounted to 24 TOE/yr, payback 27 years. 400 m2 of CORTEC evacuated tube collectors (nett area 220 m2) are used in combination with a YAZAKI absorption chiller (52 kW) and hot water storage.
During the 1987 and 1988 cooling season the system operated well. Out of a total 40.206 MJ required in August 34 percent was supplied by the installation. In September when 38.017 MJ was required, 25 percent was supplied by the installation.
At the same time, the system also supplied a large proportion of heat for the primary air post heating of the air conditioned test laboratory and for the hot water production, in August 97% of the total 80.000 MJ, in September 87% of the total 50.000 MJ.
Over the whole summer period, a solar coverage of 82% was achieved and the solar collector loop had an average solar energy conversion efficiency of 38 to 43 %.
In winter time operation the daily solar collector efficiency dropped to 25%, although still covering 22% of the winter hot water and space heating needs.
Practical experience gained by this project and useful to be considered in future realizations regard simplification of the control without or with little performance reduction. Alsothe reflecting surface with mirrors in front of the collectors has shown to be inadequate for the year round external environment conditions and has lost its reflecting characteristics in one year time. Furthermore, 5% of the collector tubes have lost their vacuum.
The construction of the storage tanks in the ground has given problems for the operation of the "solar loop". The hydraulic pressure in the loop is very low due to the low position of the unpressurized tank. This requires a circulation pump with a high static pressure at the departure from the storage tank to keep the hydraulic loop under pressure, and a pressure drop valve at the return to the storage tank. This leads to an unnecessary high electrical power consumption for the pumps, and could be partly resolved by building the storage tanks above the ground level.
The project has been technically a success, including the operation of the absorption chillers. The economical pay-back is at present about 45 years, but the potential on a medium or long term has been demonstrated.
In the framework of this contract a solar cooling plant is under construction at Pordenone to supply air conditioning to the building of CERIT (regional Centre for Technological Research). The single flat building comprises an area of 3800 m2 with laboratories and offices for 60 people.
THE SOLAR SECTION
The temperature level needed to drive the absorption machines for solar operation is in the range 80-90 deg.C. Good reliability and low maintenance for the solar section were desired: therefore the choice moved toward evacuated tubular collectors which allowed a high efficiency in the working range without problems of corrosion damage due to weathering. In fact various manufacturers gave guaranties up to 10 years concerning even the vacuum seal.
The ETC was chosen because:
- over 80 deg.C it is little sensitive to temperature increase (low slope in the efficiency curve);
- the ETC has a better efficiency for not normal incidence (high angle incidence modifier) and this means a better daily performance particularly in connection with reflector systems;
- the manufacturer offered a very favourable guaranty contract covering every risk of damage (breakage, vacuum loss, hail damage included) for a period as long as 10 years;
- the ETC is made in Europe
To enhance the solar section, the use of a planar reflector was studied: the reflector set in front of the collector array increases the solar intensity onto the collectors.
THE ABSORPTION MACHINE AND THE STORAGE
The existing plant is equipped with a four cylinder compression chiller. The load peaks are coped with by this machine.
The choice of capacity of the absorption-chiller was the minimum installed capacity, thereby having it work the whole day (24 h). This not only minimized the initial cost of the machine (whose capacity is 52 kW), but further it allows a steady operation that is very favourable for the performance.
A hot tank is also necessary to store the heat collected in order to assure the supply tothe machine during the night. Chilled water storage is also provided, whose function is to store the cold to satisfy promtly the demand, supplying the cold produced during the night or during the week-ends. As the chilled water temperature difference is limited to few degrees, instead of the hot water drop, the size of the chilled water storage is larger than the hot water one: 200 m3 and 40 m3 respectively. The chilled water storage is subdivided into two different tanks to separate sharply the supply water from the return.

Programm/Programme

ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984

Thema/Themen

3.1 - THERMAL

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

DEM - Demonstration contracts

Koordinator

Cerit SpA

EU-Beitrag

Keine Daten

Adresse

Via Villanova di Sotto 9/A
33170 Pordenone
Italien

Gesamtkosten