VOCATIONAL TRAINING BUILDING INTEGRATION OF PHOTOVOLTAICS (BIPV) TOWARDS NEARLY ZERO ENERGY BUILDINGS (NZEB)

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1 VOCATIONAL TRAINING BUILDING INTEGRATION OF PHOTOVOLTAICS (BIPV) TOWARDS NEARLY ZERO ENERGY BUILDINGS (NZEB) CHAPTER 2: SUNLIGHT/HEAT AND NZEB TECHNOLOGIES LECTURE 10: SYSTEMS FOR HVAC AND DHW

2 Content Unit 10: Systems for HVAC and DHW 2 Introduction 2.1 Heating 2.2 Cooling 2.3 Ceiling Fan 2.4 Domestic Hot Water 2

3 Reference Book MECIT, Technical Guidebook for Nearly Zero Energy Buildings,

4 2 Introduction In this section the main aspects of heating and cooling the building in the most efficient way are analysed. 4

5 2.1 Heating In NZEB the requirements for heating must be kept low. More specifically, for households the requirement based on ΚΔΠ366/2014 the yearly heating requirement must not be higher than 15kWh/m 2. 5

6 2.1 Heating For the heating of NZEB some of the recommended ways include: High efficiency boiler oil/natural gas with efficiency (βαθμός απόδοσης καύσης) > 92% at the nominal capacity of the boiler. High efficiency heat pumps in preference with an efficiency >3.5. Solar thermal heating in conjunction with a boiler or heat pump system. Their use can provide 50% conservation of conventional fuel used for heating and 80% for the use of domestic hot water. 6

7 2.1 Heating Guidelines for improved efficiency and decrease of heating consumption: Maintain the boiler (commonly every start or end of winter season) Select a 20 ºC setting for the temperature Have in mind that for every degree you decrease the thermostat you can achieve 2% reduction of heating consumption for every 8 hours of operation of the heating system. Use thermostats and timers to make use of heating only at the hours of the day necessary 7

8 2.1 Heating Seasonal Coefficient of Performance (SCOP) - This is the overall coefficient of performance of the unit, representative of the entire heating season designated (the value of SCOP corresponds to a determined heating season). It is calculated by dividing the reference annual heating demand by the annual consumption of electricity for heating. 8

9 2.2 Cooling The cooling loads of a NZEB can be extremely high especially in cases where shading measures are not appropriately taken. As a generic rule for autonomous cooling systems with power less than 12 kw, the seasonal energy efficiency is determined by their label. In larger cooling systems > 12 kw the seasonal efficiency can be calculated, while energy can be conserved with optimal design of the system, ducts and their insulation. Efficient cooling systems can be heat pumps and solar cooling with heat pump. 9

10 2.2 Cooling Seasonal Energy Efficiency Ratio (SEER) This is the overall energy efficiency ratio of the unit, representative of the entire cooling season. It is calculated as the annual cooling demand divided by the annual consumption of electricity for cooling. 10

2.3 Ceiling fan The use of celling fans at different locations of the building can assist in decreasing the energy demand for cooling, as the fans increase

11 2.3 Ceiling fan The use of celling fans at different locations of the building can assist in decreasing the energy demand for cooling, as the fans increase the movement of air within the room. Common fans are expected to be installed at a height of 2.5 m from the floor and are effective up to a distance of 1.8 m. 11

2.3 Ceiling fan It is expected that with a fan that can cover 80 % of a room then the same comfort in cooling can be achieved by increasing the air conditioning

12 2.3 Ceiling fan It is expected that with a fan that can cover 80 % of a room then the same comfort in cooling can be achieved by increasing the air conditioning unit another 2 C. Table exhibiting the area coverage of the fan and respective achieved increase of air conditioning during the summer for improved thermal comfort 12

13 2.4 Domestic Hot Water (DHW) Solar-thermal technologies make use of sunlight to heat a medium for either the provision of space heating or domestic hot water. Solar-thermal technologies are therefore very important for NZEBs in order to minimize electricity used to heat the space of the building or domestic water. In Cyprus almost all residential buildings have a solarthermal system for domestic hot water (DHW). The use of DHW in new buildings is also obligatory for new buildings used as households in Cyprus. 13

including the energy for appliances and lighting).

14 2.4 Domestic Hot Water (DHW) The yearly consumption for domestic hot water is around 15 kwh/m 2. For an energy efficient building class B this represents 10% of the total energy consumption (not including the energy for appliances and lighting). For an NZEB which has a more limited consumption for heating and cooling, the energy consumption for domestic hot water can represent the 20%. 14

2.4 Domestic Hot Water (DHW) In Australia, Cyprus, Israel and other Mediterranean countries, as well as many other countries, especially with tropical or subtropical climates, systems are

15 2.4 Domestic Hot Water (DHW) In Australia, Cyprus, Israel and other Mediterranean countries, as well as many other countries, especially with tropical or subtropical climates, systems are designed based on the principle that hot water rises. These are called thermosyphon systems, and the storage tank is almost always located outdoors, directly on top of the solar collector. 15

2.4 Domestic Hot Water (DHW) Collectors have the task of converting light as completely as possible into heat, and then of transferring this heat with

16 2.4 Domestic Hot Water (DHW) Collectors have the task of converting light as completely as possible into heat, and then of transferring this heat with low losses to the downstream system. There are many different types and designs for different applications, all with different costs and performances. 16

17 2.4 Domestic Hot Water (DHW) The main types of solar thermal systems for DHW depend on the way the medium is circulated: active in circulation (with electrification for pumps) (ηλιακών συστημάτων βεβιασμένης κυκλοφορίας) Passive in circulation (θερμοσίφωνα) Passive Active 17

18 2.4 Domestic Hot Water (DHW) Working principle of a glazed solar-thermal collector The irradiance (G 0 ) hits the glass cover. Here, even before it enters the collector, a small part of the energy (G 1 ) is reflected at the outer and inner surfaces of the pane. The selectively coated surface of the absorber also reflects a small part of the light (G 2 ) and converts the remaining radiation into heat. With good thermal insulation on the rear and on the sides of the collector using standard, noncombustible insulating materials such as mineral wool and/or CFC (chlorofluorocarbon)- free polyurethane foam sheets, the energy losses through thermal conduction (Q 1 ) are reduced as much as possible. The transparent cover on the front of the collector has the task of reducing losses from the absorber surface through thermal radiation and convection (Q 2 ). By this means only convection and radiation losses from the internally heated glass pane to the surroundings occur. From the irradiated solar energy (G 0 ), because of the various energy losses G 1, G 2, Q 1 and Q 2, the remaining heat (Q A ) is finally usable. 18

19 2.4 Domestic Hot Water (DHW) Collector efficiency coefficient The efficiency, η, of a collector is defined as the ratio of usable thermal power Q A to the irradiated solar energy G 0 per area of solar collector A: η = Q A G 0 A 19

2.4 Domestic Hot Water (DHW) 2.4.2 Collector efficiency coefficient The efficiency is influenced by the design of the collector.

20 2.4 Domestic Hot Water (DHW) Collector efficiency coefficient The efficiency is influenced by the design of the collector. The power output in Watts of a solar collector is found according to EN for solar irradiance G 0 of 700 W/m 2 and temperature difference ΔT between collector and ambient of 30 ºC. 20

2.4 Domestic Hot Water (DHW) 2.4.3 DHW system requirements in

21 2.4 Domestic Hot Water (DHW) DHW system requirements in Cyprus Ελάχιστες Απαιτήσεις Ηλιακών Συστημάτων Ηλιακοί Θερμοσίφωνες 21

22 2.4 Domestic Hot Water (DHW) DHW system requirements in Cyprus Ελάχιστες Απαιτήσεις Ηλιακών Συστημάτων Ηλιακά Συστήματα βεβιασμένης Κυκλοφορίας Στις περιπτώσεις όπου χρησιμοποιούνται ηλιακά συστήματα βεβιασμένης κυκλοφορίας η ελάχιστη επιφάνεια των ηλιακών συλλεκτών, σε τετραγωνικά μέτρα, είναι αντίστοιχη με το συνολικό αριθμό των υπνοδωματίων που εξυπηρετεί το ηλιακό σύστημα όταν η ελάχιστη ισχύς για ένα τετραγωνικό μέτρο επιφάνειας του ηλιακού συλλέκτη είναι 320 Watt. Σε περιπτώσεις όπου χρησιμοποιούνται ηλιακοί συλλέκτες διαφορετικής ισχύς από την πιο πάνω, η επιφάνεια του ηλιακού πεδίου υπολογίζεται με βάση την ακόλουθη εξίσωση: ΑΥ 320 ΕΠ = ΙΣ Όπου ΕΠ είναι η Συνολική ζητούμενη επιφάνεια ηλιακού πεδίου σε m 2, ΑΥ είναι ο Συνολικός αριθμός υπνοδωματίων, ΙΣ είναι η Ισχύς συλλέκτη που θα χρησιμοποιηθεί σε W/m 2 επιφάνειας συλλέκτη και 320 είναι τα 320 Watt, 22

23 2.4 Domestic Hot Water (DHW) DHW system requirements in Cyprus Χωρητικότητα της δεξαμενής αποθήκευσης ζεστού νερού Για συστήματα βεβιασμένης κυκλοφορίας όταν χρησιμοποιούνται για κατοικίες ή διαμερίσματα με ένα υπνοδωμάτιο καθορίζεται στα 90 λίτρα (L) Για κατοικίες και διαμερίσματα με περισσότερα από ένα υπνοδωμάτιο η χωρητικότητα της δεξαμενής καθορίζεται με βάση την ακόλουθη εξίσωση: ΧΔ = ΑΥ Όπου ΧΔ είναι η Χωρητικότητα δεξαμενής ζεστού νερού σε λίτρα L και ΑΥ είναι ο Συνολικός αριθμός υπνοδωματίων. 23

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