WidetheSEEbySuccMod
Widening the Thermal Solar Energy Exploitation
by the Successful Models
WidetheSEEbySuccMode
Project Code: SEE/A/080/2.4/X
Training Manual
Released by:
Market Operator Working Group
Deliverable Status: FINAL
Date of Preparation: 03/07/2011
WidetheSEEbySuccMod
WidetheSEEbySuccMod
CONTENTS:
Introduction
1. WidetheSEE Project
2. Technical Presentation of DHW Installations
3. Conditions of Using DHW Installations
4. Practical Application on DHW Dimensioning
Calculation, Orientation, Impact Study on the
Environment
5. Regional and National Regulatory Framework
6. Support Mechanism and Incentives
7. WidetheSEE Methodological Guide
8. Real Application
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In its recently adopted Climate and Energy Package, the European Union
has set ambitious energy and climate targets, the well-known 20/20/20 targets
to be reached by 2020. As the buildings are responsible for more that 40% of all
energy use in EU, this sector is a key area on which to focus attention.
On one hand, it is the biggest energy consumer, while on the other, it
offers a great potential for integration of small-scale heat and/or power systems
using energy from renewable sources (RES). The use of renewable energy
sources installations in the building sector will require a significant number of
highly-qualified installers capable of integrating renewables in both, the new and
the existing buildings. It will also be necessary to ensure the good functioning of
these systems after installation, as well as to ensure that they are well adapted
to the individual requirements of each customer and that the life-cycle
considerations have been taken into account.
Today’s solar heating systems not only keep swimming pools warm - they
can also heat much of your home’s water and interior space. Their popularity is
increasing for several reasons. Solar heating systems are reliable, adaptable, and
environment-friendly because they use renewable energy from the sun. Many
systems include sleek, attractive, low-relief collectors that people often mistake
for skylights.
Did you know that solar heating systems work well in many different
climates? Some applications, such as pool heating, are widely cost-effective
today. The cost-effectiveness of other applications depends on specific
circumstances, such as the type and cost of your usual source of energy. Today,
special financing is available to help you purchase the system that’s right for your
home.
A solar heating system is a substantial but rewarding investment. It can
reduce the monthly heating bill while helping to protect the environment. Being
informed and planning carefully will ensure that you’ve chosen the right system
for you and your family.
If you’d like to find out more about solar heating for homes, this course is a
good place to start. Here, you’ll find out how solar heating systems work, how
they are used, their benefits, etc. Please note, however, that this material is not
a technical guide to designing a system. For that, you’ll need to consult an
experienced solar heating contractor.
WidetheSEEbySuccMod
1. W
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ojjeecctt -- a Project for More
Solar Thermal Plants
Solar energy is clean and safe. It will always be available and it is
free of charge: the reasons for using solar energy thermally are
numerous.
In some countries in the EU, such as Greece and Austria, the use of solar
energy for heating and water heating is widespread. In other countries it is used
less. The project “Widening the Thermal Solar Energy Exploitation by the
Successful Models” – WidetheSeebySuccMod - was started to boost the
use of this environmentally friendly and sustainable source of energy in more
European countries.
The project idea comes from the visual
observation of roofs in some Greek and Austrian
cities, which show a lot of solar DHW collectors
while the roofs of similar cities in Romania, Italy,
Hungary, Slovenia, Croatia, Republic of Moldova
and Ukraine show very few. The 7th
EurObserv'ER report confirmed that efforts made
by SEE countries for development of Thermal
Solar were successful in limited number of them
and considerable disparities between them
appear. The project aims at allowing the SEE countries with limited penetration
to raise their Solar DHW Market, by:
- developing a framework of local and regional policies and financial
measures;
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- implementing installers' qualification and public awareness campaign to
change household habits and stakeholder attitudes;
- revealing and alleviating shortcomings and constraints that inhibit the
DHW market;
The purpose of the project is to activate a transfer of know-how and
experiences from SEE countries with significant penetration and a cooperation in
order to widen the use of Thermal Solar energy to cover the expected rise in
energy demand, reduce the greenhouse gas emission, and create new
employment opportunity from DHW market enlargement.
The beneficiaries of project will be regional and local authorities, Regional
and local development agencies, scientific institutions, house owners and installer
associations.
The project partners from (11) eleven
countries SEE (South-East-Europe)
 develop a common political and financial
general set-up for the successful spread
of thermal solar plants;
 develop awareness campaigns for
inhabitants and other target groups;
 have qualification campaigns for fitters;
 Investigate deficiencies and obstacles,
which jam the market for thermal solar
plants for heating and water heating in residential premises.
Thus, “Wide the See by Succ Mod” aims at covering the increasing energy
requirements by using thermal solar energy, reduce the emission of green-house
gases and create new jobs in the sustainable energy sector.
As main results and tangible legacy will be National DHW Markets Status
and Impact of raising DHW Solar on environment Reports,
Technical and training manuals for DHW Installers, Raise
Awareness Campaigns' Multimedia Materials, about 240
new DHW Systems installed in 4 SEE Countries and new 4
skilled and qualified teams to support House Owners in
acquiring, funding and installing DHW Systems,
Methodologies and procedures to make effective the fiscal
aids and subventions on behalf of House Owner, DHW
Methodological Guide and Green Paper distributed to
competent Policy Makers all over Europe.
On www.widethesee.eu there is more information to be found about the
project, which will be completed by 2012.
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‫ ٭‬Basis
Solar water heaters and solar
space heaters are made up of solar
collectors and all systems except pool
heaters have some kind of storage.
In pool systems, the swimming
pool itself is the storage and the
pool’s filtration pump circulates the
pool water through the collectors.
Active systems also have circulating
pumps and controls; passive systems
work without this added equipment.
Three types of solar collectors
are used for residential applications:
flat-plate, integral collector-storage (ICS), and evacuated-tube collectors.
Flat-plate collectors like the one shown on page 3 are the most common
type. Glazed flat-plate collectors essentially are
insulated, weatherproofed boxes that contain a dark
absorber plate under one or more glass or plastic
(polymer) covers. Unglazed flat-plate collectors are
simply a dark absorber plate, made of metal or
polymer, without a cover or enclosure. Unglazed flatplate collectors made from polymer materials are
typically used in solar pool-heating systems.
Integral collector-storage systems,
also known as ICS or “batch” systems, are
made of one or more black tanks or tubes in
an insulated, glazed box. Cold water first
passes through the solar collector, which
preheats the water, and then continues to the
conventional backup water heater. ICS
systems are simple, reliable solar water
heaters. However, they should be installed
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only in mild-freeze climates because the outdoor pipes could freeze in severely
cold weather.
Evacuated-tube
solar
collectors are usually made of
parallel rows of transparent glass
tubes. Each tube contains a glass
outer tube and metal absorber tube
attached to a fin. The fin is covered
with a coating that absorbs solar
energy well, but which inhibits
radioactive heat loss. Air is removed,
or evacuated, from the space between
the glass tubes and the metal tubes to
form a vacuum, which eliminates
conductive and convective heat loss.
In the Europe, evacuated-tube collector systems are used most frequently in
commercial applications. Most solar water heaters require a well-insulated
storage tank. Solar storage tanks have an additional outlet and inlet connected
to and from the collector. Active solar systems usually include a storage tank
along with a conventional water heater. In two-tank systems, the solar water
heater preheats water before it enters the conventional water heater. In onetank system, like the one shown on page 4, the backup heater is combined with
the solar storage in one tank.
Active solar water heaters use pumps to circulate water or a
nonfreezing heat-transfer fluid from storage tanks through the collectors. Active
systems are usually more expensive than passive systems, but they are also
usually more efficient.
Direct circulation systems use a pump to circulate household water
through the collectors and into the home; they work well in climates where it
rarely freezes.
Indirect circulation systems use pumps to circulate a non-freezing heat
transfer fluid through the collectors and a heat exchanger. This heats water that
then flows into the home. Indirect systems are popular in climates prone to
freezing temperatures.
Passive direct solar water heaters, like the one shown on page 5,
move household water or a heat-transfer fluid through the system without using
pumps or electricity. Passive systems work during power outages, but they
should not be used in climates where temperatures often go below freezing.
Passive systems are typically less expensive to purchase and maintain than other
types of solar systems. They are also inherently more reliable and may last
longer. However, passive systems are not usually as efficient as active systems.
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ICS passive solar systems may be best in areas where temperatures rarely
go below freezing. They are also good in households with significant daytime and
evening hot-water needs.
Thermosyphon systems work because water
flows through the system when warm water rises as
cooler water sinks. In this system, the collector must
be installed below the storage tank so that warm
water will rise into the tank. These systems are
reliable, but contractors must pay careful attention
to roof design because the water in the storage tank
is heavy. Thermosyphon passive solar systems are
usually less expensive than active systems, but more
expensive than ICS systems.
‫ ٭‬Functioning of a solar plant
Solar water heating systems are climate and site specific appliances.
Different types of solar systems are installed around the world in accordance with
regional weather and water quality conditions. System performance varies as a
function of the household hot water load, including daily showers, laundry and
kitchen uses, average ground water and ambient air temperatures, the home’s
roof pitch and orientation, and, of course, the seasonal intensity of solar
radiation.
These variables, some of which change from home to home on the same
neighborhood street, will determine how
much energy and money your STS system
will save on an annual basis.
The key components in the STS solar
water heating system include the Solar
Thermal Systems solar collector, solar
storage tank with integral heat exchanger,
circulation pump, differential thermostat,
expansion tank, pressure gauge, mixing
valve and the non-toxic propylene glycol
heat transfer fluid (HTF).
Simply stated, when the sun is
shining, heat energy is absorbed by the
solar collector’s absorber plate and
transferred to the HTF circulating through
the solar collector. The system pump
circulates this heated fluid through the collector piping and integral tank heat
exchanger located in the bottom of the storage tank. As the HTF passes through
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the heat exchanger the heat in the fluid is transferred by conduction to the
potable water in the solar storage tank. As this process is continuously repeated,
the water temperature in the solar storage tank rises.
The circulating pump in a solar water heating system may be favorably
compared with the human heart. To continue the analogy, the differential
thermostat or controller, is the brain of the system. The controller uses
thermistors or sensors to constantly monitor the temperature difference between
the hottest and coldest points in the system and to automatically turn the
circulating pump on and off throughout the day. When the solar collector
absorber plate is approximately twelve degrees hotter than the temperature in
the bottom of your solar storage tank, the controller will turn the circulating
pump on. When the temperature difference has been reduced to four degrees,
the controller automatically turns the pump off.
Propylene glycol can degrade over time. The process of degradation is
accelerated in presence of oxygen and/or heat. We strongly encourage to be
established a preventative maintenance schedule with the installation contractor.
The HTF pH level must be maintained between 8 and 10 in order to prevent
glycol oxidation and corrosion of the collector piping.
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3. Conditions of Using the DHW
Installations
‫ ٭‬Sun radiation
Understanding solar
thermal systems requires
the knowledge of several
energy terms and physical
principles.
Terms and Principles
Insolation
is
the
amount
of
the
sun’s
electromagnetic
energy
that “falls” on any given
object. Simply put, when
we are talking about solar
radiation, we are referring to insolation. In general, for a good insolation (at sea
level) an object will receive a minimum 200 w/m2 and maximum of around 1000
w/m2 at high noon on a horizontal surface under clear skies on June 21 (the day
of the summer equinox).
On the surface of the earth, insolation varies over time because of the
planet’s daily rotation, tilted axis and elliptical orbit around the sun. Imagine the
sky as a dome (sky dome) with
the horizon as its edge.
This perceived path and its
variations over time can be
plotted as in figure below, which
shows the annual sun path from
the perspective of 28˚ north
latitude. The figure illustrates the
seasonal changes in the sun's
path for a given location. It
shows that the winter the sun
rises in the Southeast and has a
relatively short path and rises to
a shallow 39˚ angle above the
horizon at noon. In the
summertime, the sun rises in the Northeast and has a longer path and rises to a
much higher angle above the horizon.
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• Conduction
Conduction occurs when a solid material is heated. Molecules exposed to a
heat source become energized. These energetic molecules collide with
neighboring, less-energetic molecules, transferring their energy. The greater the
energy transfer ability of the solid’s molecules, the more energy they can transfer
and the better the solid’s conductivity. Copper has high conductivity while glass
has low conductivity.
• Convection
Like conduction, convection occurs by molecular motion but in a fluid (such
as a gas or liquid), rather than in a solid. When a gas or liquid is heated, the
energized molecules begin to flow. On earth, where gravity is a factor, the
heated, less-dense fluid flows upward as cooler, more compact fluid moves
down. This process of displacement continues as long as the heat source
remains.
• Radiation
Radiation occurs not by molecular action but rather by emission of
electromagnetic waves, generally in the invisible, infrared spectrum. Because
radiation does not rely on the presence of matter (molecules) for transport, it can
occur in a vacuum. Just as the sun radiates to the earth, a warm object on earth
will radiate infrared waves at night to objects in deep space. All objects with heat
radiate to objects with less heat that are in a direct path.
Some materials absorb more insolation than others. The more absorptive
materials are generally dark with a matte finish, while the more-reflective
materials are lighter colored with a smooth or shiny finish.
The materials used to absorb the sun's energy are selected for their ability
to absorb a high percentage of energy and to reflect a minimum amount of
energy. The solar collector's absorber and absorber coating efficiency are
determined by the rate of absorption versus the rate of reflectance. This in turn,
affects the absorber and absorber coating's ability to retain heat and minimize
emissivity and reradiation. High absorptivity and low reflectivity improves the
potential for collecting solar energy.
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Basic ideas to remember:
– Exchange of energy models:
Conduction - Fourier lay: flow through a material media with out translation of
material:
q = k/e · ΔT)
Convection - Newton lay, convection is influenced by mass transport and energy:
Q = h · (TS – Tinf)
Radiation - Emission of energy by electromagnetic
waves).
– Considerations:
Spectra
Absorption, Reflexion, Transmission
E=A+R+T
‫ ٭‬Positioning the Panels
South Facing Roofs
Positioning the collectors is important for optimum
performance. Collectors should ideally be mounting at
an angle of between 30 degrees and 60 degrees on a
south facing position that is not shaded by
overhanging trees, buildings, or structures. Good
results can be obtained by positioning the panels
facing anywhere in an arc between south west and
south east but due south facing provides optimum
performance.
North Facing Roofs
It is not generally recommended that you install the
panels on North facing roofs in the Northern
Hemisphere. South of the equator, north will provide
the optimum performance and south facing the worst
performance.
East / West Facing Roofs
Good results can be obtained by splitting the collector
array on East / West elevations but this should only be
used when it is not possible to have a mainly southern
position for the collectors. If you are installing an East /
West split system you have to double the number of
panels that would normally be required, for example a 2 panel system would
require 2 panels on the east and 2 panels on the west.
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East / West Facing Roofs (Alternate Configuration)
Another option is to oversize the collector area on the side of the roof chosen to
mount the collectors. For example If 2 panels would have been adequate had the
roof orientation been south, then 3 collectors would be required on either the east
side or the west side depending on which received the most sunlight.
Basic terms to remember:
Inclination - Angle between the collector surface and the horizontal at that point.
Azimuth - Angle between the horizontal projection of the perpendicular to the
collector surface and the line that goes through it and the geographical south
(meridian)
Incidence - Angle between the solar radiation (lien sun collector) and the
perpendicular to the collector surface (depends on hour, day, collector tilt)
Solar high - Angle between the solar radiation and the horizontal surface
(depends on hour and latitude)
‫ ٭‬Integration of solar system
Standardization
Solar thermal heating systems should be designed for reasonable
production numbers in order to achieve competitive costs. Concepts that meet a
large variety of requirements widen the range of application and give access to a
larger market (example: a modular design which is optionally available with an
optimized integrated auxiliary heater, but can alternatively be combined with an
existing boiler or a concept which can often be used in conjunction with an
existing water heater store, but which is also a competitive solar heating system
in a new house).
Flexibility due to modular design might help bridging the gap between the
need for a high degree of prefabrication and the restrictions imposed by the
large diversity required by the market.
Simplification and reduction
Systems should be designed for easy
installation. This includes the technical
integration in an existing heating system.
It is expected that the size of the solar
heating systems in one family houses
increases. Therefore the reduction of the
amount of material used will have a crucial
impact on both the cost and the amount of
embodied energy used. Besides increasing
efficiency, ways to reduce the amount of
material used are:
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- optimize the storage of solar heat by minimizing the storage of heat from
the auxiliary heater;
- use lean concepts, like non-pressurized tanks or recombine the functions
of several components in one component.
Reduced maintenance
Several concepts of the new generation of systems aim at reducing
maintenance. Besides autodiagnostics and a design with few, but reliable,
components the focus lies on avoiding problems with glycol decomposition by
using an appropriate system concept. Several of the systems, representing the
new generation, follow this track. However, different approaches are possible.
Improved efficiency
Economic ways to increase
the system efficiency are used in
several of the new system
concepts like the optimization of
the storage management and an
efficient
utilization
of
the
auxiliary heater. These concepts
are the compact combi-system
unit with gas auxiliary heater,
the unit with pellets auxiliary
heater and the compact heating
unit for solar domestic hot water
(SDHW) preparation.
The energy saved with
reference to a conventional water heater, depends on the climate, the collector
layout, the sizing and system design, as well as the components and their
maintenance.
Therefore, it is essential that the best relationship between the costs, the
system size and the needs must be founded during the project design phase.
This must also include the most effective design of all the components, so that
solar energy collection and storage is optimal, solar and back-up energy supplies
are dissociated, solar energy is used in priority and the back-up energy supply is
only used as a complementary energy source.
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4. DHW Dimensioning Calculation
‫ ٭‬Analysis of the domestic hot water demand
Domestic hot water supply systems using solar energy require an auxiliary
source of energy for the following reasons:
- maintaining the required water temperature for the hot water needed, as
the solar installation is generally sized to cover only part of the needs; and
- maintaining the required water temperature in order to avoid bacteria,
particularly legionelas.
Generally speaking, in order to limit the development of these bacteria,
water stagnation in dead-end piping should be avoided. The temperature of the
hot water leaving the storage tanks should be at least 60°C, and in the case of a
circulation loop, the return temperature should be at least 50 °C.
The users should always be protected from scalding at the supply points,
where the water temperature should not be greater than 50°C. The provider of
the hot water has to ensure the temperature reached at the consumer level
between 45° and 55°C.
Hot water production is amongst
the most efficient solar energy
applications, particularly for collective
systems in residential and tertiary
buildings where the hot water demand
is important and steady; notably, for
collective housing, hotels and health
establishments. These requirements for collective buildings (housing, hotels,
hospitals, etc.) show a growing demand for hot water, not only for the sanitary
needs but also for the domestic tasks. The usefulness of a hot water supply
system is characterized by the availability of the hot water, in a sufficient
quantity, at a given temperature, when it is needed, and at a cost as low as
possible.
‫ ٭‬Sizing of surface’s collectors and tank
The type, complexity, and size of a solar water heating system are mostly
determined by:
- temperature and amount of the water required from the system;
- changes in ambient temperature and solar radiation between summer and
winter;
- changes in ambient temperature during the day-night cycle;
- possibility of the potable water or collector fluid overheating;
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- possibility of the potable water or collector fluid freezing.
The minimum requirements of the system are
typically determined by the amount or temperature of hot
water required during winter, when a system's output and
incoming water temperature are typically at their lowest.
The maximum output of the system is determined by the
need to prevent the water in the system from becoming too
hot or, in the systems that overheating is avoided, the
desire to waste money on unneeded components.
A flat plate collector is essentially an absorbing
surface exposed to solar radiation. The absorbing surface
transfers the heat produced by absorption and in heating, it
emits thermal radiation at a higher wavelength (Stefan-
Boltzman's Law).
If the absorber is in direct contact with the ambient air, there will be
important heat losses by convection as well as by radiation. A thermal balance
will be established between the absorber and the ambient air. Therefore, little
energy will be collected. In order to reduce the losses from the back of the
collector, the absorber is placed in a box in which the inside surfaces are covered
with thermal insulation (glass wool or expanded synthetic materials, for
example).
The thermal insulation in front of the absorber is composed of a material
that is opaque to thermal radiation but transparent to solar radiation. Glass and
certain synthetic materials are transparent to solar radiation and opaque for the
infrared radiation. Therefore, they are used as transparent covers for solar
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collectors. In the case of a solar collector with a transparent cover: the cover
absorbs the thermal radiation emitted by the absorber, heats up and radiates
heat from both sides. As a rough estimation, half of the radiation is diffused to
the outside and the other half is returned to the absorber. This is the greenhouse
effect.
The glazing also limits heat loss by convection, as the thermal transfer
between two surfaces that are separated by a layer of motionless air are mainly
due to conduction and the motionless air makes effective thermal insulation. The
quality of the insulation increased with the thickness of the air layer between the
two surfaces, as long as the heat transfer is by conduction (2 to 3 cm). If the
space between the two surfaces is too important, natural convection is set up
and has the opposite effect.
Another way of reducing collector heat loss is to add a selective coating to
the absorber. This coating offers an absorption coefficient as high as possible for
radiation in the solar spectrum (less than 2,5 mm) and an emission coefficient as
low as possible in the infrared, that corresponds to the radiation of the absorber
(wave lengths greater than 2,5 mm). Such selective coatings are made by a
chemical deposit on the absorbing surface. Finally vacuum tube collectors make it
possible to reduce heat losses by convection, as the absorber is placed inside a
glass tube from which the air has been withdrawn.
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5. Regional and National Regulatory
Framework
‫ ٭‬European Regulatory Framework
Certification in general refers to
the confirmation of certain
characteristics of an object, person, or organization. This confirmation is usually
provided by some form of external review, education, or assessment.
Product Certification is the process of certifying that a certain product
has passed performance and quality assurance tests or qualification requirements
stipulated in regulations or that it complies with a set of regulations governing
quality and minimum performance requirements.
Why do we need Standards and Certification in general?
Industry: In order to avoid market barriers, bad quality products, bad
reputation and to avoid bad impact on market development.
User: Giving the possibility to choose quality products.
Authorities: Opportunity to check the requirements set in regulations
and subsidy schemes.
Why do we need European Standards and Certification?
Industry: In order to avoid market barriers,
which avoids also large quantity of time and money for
testing in many different countries to many different
standards, leading to one large market
User: Due to larger production volume & lower
testing costs results cheaper quality products
Authorities: If Standards are available there is
no need for making special national standards.
EN 12975 refeeres to Collectors
Part 1 - General Requirements; Part 2 - Test Methods
- Durability, reliability, safety, performance of liquid heating collectors, glazed &
unglazed, “low” temperature
Not included: ICS, (tracking concentrating collector), acc. ageing, air collectors
EN 12976 refeeres to Factory made systems
Part 1 - General Requirements; Part 2 - Test Methods
- Durability, reliability, safety, performance of “kits”
Not included: Tests for DHW+SH (combisystems), air systems, cooling
EN 12977 refeeres to Custom built systems
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Part 1 - General Requirements; Part 2 - Test Methods; Part 3 - Performance
characterization of stores for solar heating systems
- Durability, reliability, safety, performance of custom built systems and
components (hot water store, differential controller, etc.)
Not included: Tests for DHW+SH (combisystems), air systems, cooling, high
temperatures, etc.
Current standards – status
EN 12975-1/2
Collectors
Revised – formal vote
after TC 312 meeting
01-2005
EN 12976-1/2:
Factory made systems
Revised – formal vote
after TC 312 meeting
01-2005
ENV 12977-1/2/3
Custom built systems
Restructuring and
expansion/ Significant
revision
In order to obtain a certification of a collector, the installer has to be make
the description of the collector (collector, absorber, insulation and casing,
limitations, kind of mounting), collector efficiency curve (test method, description
of the calculation, instantaneous efficiency curve based on aperture and absorber
area and mean temperature of heat transfer fluid, efficiency curve for the
determined coefficients and for an assumed irradiation of 800 W/m based on
aperture area).
The tests under the EN 12975 include Thermal Performance Testing (test
under steady state conditions (indoor and outdoor) test under quasi-dynamic
conditions, pressure drop, effective thermal capacity) and Durability and
Reliability Testing (internal pressure test, high temperature resistance test,
exposure test, external thermal shock tests, internal thermal shock tests, rain
penetration test, Internal pressure test (retest), mechanical load test (positive
pressure test of the collector cover, negative pressure test of fixings between the
cover and the collector box, negative pressure test of mountings), stagnation
temperature and final inspection).
‫ ٭‬Energy saving
The amount of heat delivered by a solar water heating system depends
primarily on the amount of heat delivered by the sun at a particular place (the
insolation). The insolation can be in temperate areas where the days are shorter
in winter for 3.2 kW·h/m2 per day. Even at the same latitude the average
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insolation can vary a great deal from location to location due to differences in
local weather patterns and the amount of overcast. Useful calculators for
estimating insulation at a site can be found with the Joint Research Laboratory of
the European Commission.
Below is a table that gives a rough indication of the specifications and
energy that could be expected from a solar water heating system involving some
2 m2 of absorber area of the collector, demonstrating two evacuated tube and
three flat plate solar water heating systems. Certification information or figures
calculated from those data are used. The bottom two rows give estimates for
daily energy production (kW·h/day) for a temperate scenario. These estimates
are for heating water to 50˚C above ambient temperature.
With most solar water heating systems, the energy output scales linearly
with the surface area of the absorbers. Therefore, when comparing figures, can
be take into account the absorber area of the collector because collectors with
less absorber area yield less heat even within the 2 m2 range. Specifications for
many complete solar water heating systems and separate solar collectors can be
found.
Daily energy production (kWth·h) of five solar thermal systems
The evac tube systems used below both have 20 tubes
Technology used
Flat plate Flat plate Flat plate Evac tube Evac tube
Direct
Thermo- Indirect Indirect
Direct
Configuration
active
siphon
active
active
active
2
Overall size (m )
2.49
1.98
1.87
2.85
2.97
2
Absorber size (m )
2.21
1.98
1.72
2.85
2.96
Maximum efficiency
0.68
0.74
0.61
0.57
0.46
Energy production
(kW.h/day):
5.3
3.9
3.3
4.8
4.0
- Insolation 3.2 kW.h/m2/day
(temperate)
The figures are fairly similar between the above collectors, yielding some
4 kW·h/day in a temperate climate when using a collector with an absorber area
of about 2m2 in size. In the temperate scenario this is sufficient to heat 200 liters
of water by some 17 degrees C.
Many thermosiphon systems are quite efficient and have comparable
energy output to equivalent active systems. The efficiency of evacuated tube
collectors is somewhat lower than for flat plate collectors because the absorbers
are narrower than the tubes and the tubes have space between them, resulting
in a significantly larger percentage of inactive overall collector area. Some
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methods of comparison calculate the efficiency of evacuated tube collectors
based on the actual absorber area and not on the 'roof area' of the system as
has been done in the above table. The efficiency of the collectors becomes lower
if one demands water with a very high temperature.
‫ ٭‬Laws and Regulations on Civil Construction
The local laws and regulations on civil constructions vary from country to country.
The general tendency in the region is to transpose the EU directives and adapt
the EU standards. However, the Manual encourages you to pay attention to the
local requirements. (Chapter to be developed by the country’s participant in the
project)
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6. Support Mechanisms and Incentives
‫ ٭‬What does profitability mean?
In sunny, warm locations, where freeze protection is not necessary, an ICS
(batch type) solar water heater can be extremely cost effective. In higher
latitudes, there are often additional
design requirements for cold weather,
which add to system complexity. This
has the effect of increasing the initial
cost (but not the life-cycle cost) of a
solar water heating system, to a level
much higher than a comparable hot
water heater of the conventional type.
The biggest single consideration is
therefore the large initial financial
outlay of solar water heating systems. Offsetting this expense can take several
years and the payback period is longer in temperate environments where the
insolation is less intense.
When calculating the total cost to own and
operate, a proper analysis will consider that
solar energy is free, thus greatly reducing the
operating costs, whereas other energy sources,
such as gas and electricity, can be quite
expensive over time. Thus, when the initial costs
of a solar system are properly financed and
compared with energy costs, then in many
cases the total monthly cost of solar heat can be less than other more
conventional types of hot water heaters (also in conjunction with an existing hot
water heater). At higher latitudes, solar heaters may be less effective due to
lower solar energy, possibly requiring larger and/or dual-heating systems. In
addition, federal and local incentives can be significant.
The calculation of long term cost and payback period for a household SWH
system depends on a number of factors. Some of these are:
- price of purchasing solar water heater (more complex systems are more
expensive);
- efficiency of the purchased SWH system;
- installation costs;
- support mechanisms, existent government subsidy, fiscal incentives, etc. for
SWH;
- price per kW·h for electricity and/or fuels replaced;
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- energy (kW/h, m3, tones, etc.) used per month by a household;
- annual tax rebates or subsidy for using renewable energy;
- annual maintenance cost of a SWH system;
-savings in annual maintenance of conventional (electric/gas/oil) water
heating system, etc.
The table below reflects the costs and the payback period. It does not take
into account annual maintenance costs, annual tax rebates and installation costs.
However, it gives an indication of the total cost and the order of magnitude of
the payback period. The table assumes an energy savings of 200 kW·h per
month (about 6.57 kW·h/day) due to SWH. The payback may vary greatly due to
regional sun, extra cost due to frost protection needs of collectors, household hot
water use etc. Therefore, more information may be needed to get accurate
estimates for individual households.
INSERT THE TABLE HERE
The solar installations costs and the support mechanisms and
incentives will vary from country to country. The Manual encourages
each partner to the project to insert relevant information for their
region.
‫ ٭‬Forecast of solar installations costs
‫ ٭‬Support mecanisms and incentives
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7. WidetheSEE Methodological Guide
The differences presented by
European states with reference to
the utilization of solar thermal
energy, as well as the high
potential
presented
for
the
European
economy
by
the
widening of this market, present a
challenge for Europe in general
and the SEE area in particular.
This Methodological Guide aims at
address the challenges.. This
contribution is derived from
successful experiences that have been identified in the framework of the
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The areas of interest of this guide cover a wide range, including the public,
private, industry sectors, solar plants and public utilities, like district heating.
The target audience of the Methodological Guide is large, including citizens,
households, property owners, policy makers, local and regional authorities,
energy service companies, technical experts ad institutions, etc.
Thus,
the
project
implementation phase needs
to deal with different issues
ranging from participatory
processes
and
awareness
campaigns for making the
scope of the project well
known and understood by the
target
audiences,
the
application or use of financial
incentives
both
for
the
adoption of the project by the
end users and the necessary
investments, the training services as well as support services associated with the
overall project and the overall evaluation of the project implementation in order
to address possible risks that could jeopardize the overall project implementation.
The Methodology Guide presents guidelines related to the above phases
that may be utilized by the different target audiences in order to ensure an
efficient project implementation and the resulting widening of the SEE solar
thermal market.
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The project implementation phase needs to deal with different issues
ranging from participatory processes and awareness campaigns for making the
scope of the project well known and understood by the target audiences, the
application or utilization of financial incentives both for the adoption of the
project by the end users and the necessary investments, the training services, as
well as support services associated with the overall project and the overall
evaluation of the project implementation in order to address possible risks that
could jeopardize the overall project implementation.
6.1
Participation and Awareness Guideline
Guideline Title
Participation and Awareness
Guideline Code
G.3.1
Purpose of the Guideline
To promote the project principles towards the targeted audiences. To involve the
stakeholders in an area.
Guideline
The information provided by the communication events of the project should be
accurate, identifying the actual situation with reference to solar energy
technologies and presenting the real overall potential of these technologies.
6.2
FINANCIAL INCENTIVES GUIDELINE
Guideline Title
Financial Incentives
Guideline Code
G.3.2
Purpose of the Guideline
To utilize the available financial tools for project financing and relevant
investments. To establish new tools in order to promote the widening of the
market
Guideline
The above mechanisms could be applicable at a local, regional or national level.
Projects involving policy makers could utilize subsets of such mechanisms in
order to mix and match them into financing mechanism bundles applicable in
their regions and associated with the individual profile of their citizens.
6.3
TRAINING AND SUPPORT GUIDELINE
Guideline Title
Training and Support
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Guideline Code
G.3.3
Purpose of the Guideline
To identify the needed services in terms of professional training and support
towards the end users of solar thermal energy technologies
Guideline
Train the different stakeholders associated with the solar thermal market. This
includes local authorities, policy makers, end users, etc. They should be trained
on the overall framework of the solar thermal technology market, as well as on
the different tools that may be used for its adoption.
Training professionals on one hand and the different stakeholders involved in the
promotion and adoption of solar thermal energy applications on the other is
expected to generate the needed bundle of services for the life cycle support of
solar thermal systems towards the end users.
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8. Real Application
Except in rare cases, it will be insufficient to install a SWH system with no
electrical, gas or other fuel backup. Many SWH systems (e.g. thermosiphon
systems) have an integrated electrical heater in the integrated tank. Conversely,
many active solar systems incorporate a conventional "geyser". Electrical or other
backup heating ensures a reliable supply of hot water and ensures control of
legionella risks when heated to the base.
The temperature stability of a system is dependent on the ratio of the
volume of warm water used per day as a fraction of the size of the water
reservoir/tank that stores the hot water. If a large proportion of hot water in the
reservoir is used each day, a large fraction of the water in the reservoir needs to
be heated. This brings about large fluctuations in water temperature every day,
with risks of over- or under-heating. Since the amount of heating that needs to
take place every day is proportional to the hot water use and not to the size of
the reservoir, it is necessary to have a three times larger than the daily hot water
usage. A larger reservoir decreases the daily fluctuations in hot water
temperature.
If ample storage is pre-existing or can otherwise be reasonably acquired,
a large SWH system is more efficient economically than a small system. This is
because the price of a system is not linearly proportional to the size of the
collector array, so the price per square meter of collector is cheaper in a larger
system. If this is the case, it is worth using a system that covers nearly all of the
domestic hot water needs rather than a small fraction of the needs. This
facilitates the cost recovery.
Not all installations require new replacement of solar hot water stores.
Existing stores may be large enough and in suitable condition. Direct systems can
be retrofitted to existing stores, while indirect systems can be sometimes
retrofitted using internal and external heat exchangers.
The installation of a SWH system needs to be complemented with
efficient insulation of all water pipes connecting the collector and the water
storage tank, as well as the storage tank (or "geyser") and the most important
warm water outlets. The installation of efficient lagging significantly reduces the
heat loss from the hot water system. The installation of lagging on at least two
meters of pipe on the cold water inlet of the storage tank reduces heat loss, as
does the installation of a "geyser blanket" around the storage tank (if inside a
roof). In cold climates, the installation of lagging and insulation are often
performed even in the absence of a SWH system.
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A. Collector Assembly
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B. Roof Installing
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