On Internet we can find free tools for basic or low complexity solar systems dimensioning and for certain components or accessories estimation.

Sopelia research team has carried out an exhaustive search and testing from which a new corporate website section called Free Solar Tools has been created.

Selected tools were classified into 4 categories.

Today we will analyze the third of them: Solar Thermal.

In first category we have already analyzed tools to obtain data about solar resource and other variables to be considered in energy estimation solar system will provide in our location.

In the second category we have analyzed tools to calculate the “load”, ie the energy demand to be met.

Now we are going to analyze tools to solar thermal system dimensioning and others to estimate individual components of a system.

The order of the tools is not random. We have prioritized the most intuitive, the most universal and those that can be used online without download.

For this third category our selection is as follows:

1) Solar Thermal Calculator

Approximate calculation tool from which budget, production data and system performance study is automatically obtained.

A Navigation Guide and Manuals can be found at page bottom.

2) Simulation for Solar Thermal System Pre-design

Online application based on the TSOL software that allows solar energy system simulating to ACS and ACS + heating contribute.

Available in German, English, Spanish and French.

3) Solar Fraction Calculation

Free download program developed by IDAE (Institute for Energy Diversification and Saving) and ASIT (Solar Thermal Industry Association) that allows to define a wide variety of solar systems introducing a minimum of project parameters, associated to each system configuration; and in this way, obtain solar system coverage on ACS and pool conditioning energy demand.

4) Solar Expansion Vessel Calculation

Tool developed to calculate solar expansion vessel volume.

Volume values (total circuit, solar collectors, pipes), Maximum system temperature (ºC), Glycol concentration (%), Height between expansion vessel and system highest point (minimum value 1 Bar) and safety valve Pressure setting must be introduced.

5) Thickness Insulation Pipes Calculation

Calculator that allows to estimate minimum and more economical water pipes insulation thickness.

Pipe Grade and Size, Insulation Material, Humidity and Temperature (Internal and Ambient) must be entered.

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Thermal solar collector is responsible for capturing solar radiation and converting its energy into heat energy.

A body exposed to the sun receives an energy flow Er and heats up.

Simultaneously, thermal losses occur due to radiation, convection and conduction, which grow as the body temperature increases.

There comes a time when thermal losses Ep equals the gains due to the incident energy flow, reaching the so-called equilibrium temperature:

 Er = Ep

The equilibrium temperature of the collectors is usually between 100º and 150º C under normal conditions of use and for irradiation values in the order of 1,000 W / m2.

If it is possible to continuously extract a part of the heat produced Ee to take advantage of it as usable energy, the equilibrium conditions change:

Er = Ep + Ee

Ep is now smaller because a part of the energy received Er is tapped Ee.

The body has become a solar thermal collector.

If we want to increase Ee we have two options: reduce thermal losses Ep or increase energy flow Er.

First option involves collector design and construction improving in order to reduce losses.

For the second option is used the concentration technique, which by some optical system concentrates the solar flux on a smaller surface so that as the area decreases, the intensity increases.

In a solar collector the energy is extracted through a fluid called heat carrier.

The greater the difference between operating temperature and ambient temperature, the greater the thermal losses and thus the lower energy amount that heat transfer fluid will be able to extract.

The collectors must be operated at the lowest possible temperature, provided that temperature is sufficient for the specific use in each case.

This is because collector efficiency decreases as the operating temperature increases.

Improved insulation helps thermal losses reduce.

Reflection losses are due to transparent cover that usually exists in almost all collectors.

It will be necessary to properly orient the collectors so that they receive the greatest radiation amount possible during the period of use.

The question: which is the best collector ?

A priori has no answer.

It will depend on system location and energy demand that is intended to be met.

There are many types of solar collectors, but there are two large groups: unconcentrated collectors and concentrated collectors.

Solar thermal collectors according to their working temperature:

1) Low temperatura

1.1) Flate: protected and not protected

1.2) Vacuum tubes: direct flow, heat pipe and solar concentrator CPC)

2) High temperatura

2.1) Parabolic Cylinder

2.2) Central receiver system

2.3) Parabolic disks

2.4) Solar chimney

3) Other collectors

3.1) Rubber

3.2) Spherical

3.3) Conical

In next posts we will analyze in detail each collector type.

This content was extracted from the Solar Thermal Energy Technical-Commercial Manual and is part of Solar e-learning.

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Solar thermal energy systems for domestic applications will be increasingly present in the built landscape and will be promoted by regulations such as solar ordinances or future building technology standards.

The most basic system is the compact equipment called thermosiphon, which incorporates all subsystems and where the fluid circulates naturally (difference in densities).

Solar thermal systems use the sun’s rays to get hot water or air.

Special plates, called collectors, concentrate and accumulate Sun heat and transmit it to the fluid we want to heat.

This fluid can be home’s drinking water or home’s heating or cooling hydraulic system.

Generally a thermal solar energy system is constituted by several subsystems, which in turn can be considered as interdependent systems connected to each other.

However, sometimes the same physically independent element performs several functions within the solar system.

These different subsystems are:

a) Capture system: composed of solar collectors. They are responsible for receiving the solar radiation and transmit it to the fluid that circulates inside.

b) Accumulation system: composed of one or more deposits to accumulate the hot water generated up to the moment of its use.

c) Hydraulic system: composed of the pumps and pipes through which the working fluid circulates. A primary circuit transports the energy captured to the accumulator. The circulation of the fluid through the pipes is performed by a circulation pump or by natural circulation.

d) Exchange system: exists in case the fluid flowing through the solar collectors is not the same as the one used by the user; for example when there is frost risk or user fluid can damage the solar system. The exchanger can be part of the same accumulator or located outside.

e) Control system: in pumps forced circulation systems will be in charge to start and stop them. Different components system actuation (motorized valves, pumps, etc.) is done through control mechanisms.

f) Auxiliary energy system: generally solar system economic viability requires that total energy demand cannot be met with solar input at all times. The energy produced by solar system depends on climatic conditions and that is why an auxiliary energy production system is available. These support equipment complement the solar system in order to ensure at all times hot water service continuity.

Solar thermal systems have a great similarity with conventional thermal systems.

In fact, they share all their components (pipes, protection mechanisms, accumulation tanks, exchangers, pumping groups, insulation) except one: solar collectors.

This content was extracted from Solar Thermal Energy Technical & Commercial Manual and is part of Solar e-learning.

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Solar Layout is the App for collectors and solar modules on site positioning.

This is the most intuitive Solar App of the market.

To use it on field is not necessary to have an Internet connection because it works from place latitude, obtained by GPS.

Today we will check solar thermal energy part.

To begin press left command shown in initial screen with the house, the solar collector and the user taking a hot shower.

If our Smartphone GPS is not enabled, the App will ask us to activate it to locate our position.

Intermittent earth planet image immediately appear with the legend “Localizing”.

When our device GPS have located our position, the following screen appears to confirm it.

By confirming our location the Solar Equipment Use Menu displays.

There are 3 applications in the Menu:

1- Hot water: represented by a shower image
2- Heating: represented by a radiator image
3- Outdoor pool conditioning: represented by a pool ladder image.

By selecting one of the 3 applications, Options Menu will display.

There are 3 variables in the Menu:

1- Inclination: represented by collector and angle image
2- Orientation: represented by collector and cardinal points image
3- Distance: represented by 3 collectors rows image.

By pressing the Inclination option, we get recommended inclination value for location and solar application selected, accompanied by some Tips considering collector type used.

Pressing Orientation option, we obtain description of procedure to fix collectors orientation and access to recommended compass App discharge, if we don´t have it.

Pressing Separation option, the Kind of Surface Menu is displayed for us to select the appropriate option (Horizontal / Non horizontal).

If the surface on which the collectors will be placed is horizontal, we only must enter Collector Height in cm data.

If the surface on which the collectors will be placed is non horizontal, in addition to Collector Height in cm data, we must enter Surface Inclination Angle data.

We will enter a positive value if it matches the collector inclination direction and a negative value if it is different.

In this way we obtain the Separation (distance) between collector’s rows in meters.

Pressing i button Tips related to shadows and singular locations (snow, desert and rain areas) are deployed.

Download Solar Layout and placed solar thermal collectors on site in the most intuitive way with Sopelia.

Hydraulics is the physics field that studies fluid mechanics and is divided into Hydrostatic (liquids at rest) and hydrodynamics (liquid in motion).

density of a body d is called the mass m and volume V ratio:

d = m / V

specific gravity pe is the weight (= m g.) and volume ratio:

pe = m. g / V

Fluids (liquids and gases) always exert a pressure pr in all directions.

The pressure is the quotient between a force f (the exerted by the fluid) and the surface area S acted upon by this force:

pr = f / S

The pressure unit in the SI is the Newton divided by m2 (N / m2) and is called pascal.

Pressure exerted by gravity and the forces tending to compress the fluid is called static pressure.

The pressure resulting from movement of a fluid is called dynamic pressure.

Knowing the density or specific gravity of a fluid we can find the static pressure due to gravity at any depth h from either of the following two formulas:

pr = d. g. h

pr = pe. h

The pressure difference is equal to the depths difference h between 2 points or vertical distance between them.

A typical static pressure, is the atmospheric pressure produced in all directions on the bodies placed on earth surface due to the large air column above them. The result of this all directions atmospheric pressure action produces no net force pushing the body to one side, tends to compress it.

In the case of a container, the atmospheric pressure acts inside and outside and therefore their actions cancel each other.

We are interested in knowing the excess pressure above atmospheric pressure that may be inside the container (tanks or pipes) through measuring devices (manometers).

If air can freely enter and leave a container through the edge of the lid, the liquid surface will only be subjected to atmospheric pressure. It is an open or non pressurized reservoir.

If we measured pressure at different heights in the tank with a manometer it will be equal to zero at the surface and maximum at the bottom.

If the container is now sealed and subjected to additional pressure p, transmitted through the pipes that communicate with distribution circuit; the measurement is equal to the previous one but increased in the value of p. Usually the small pressure difference caused by the height difference is negligible compared to the overall circuit pressure p.

Archimedes’s theorem allows us to know a body weight when it is immersed in a liquid.

This theorem can be applied to a same liquid portion.

Suppose that a liquid portion suffer a slight temperature increase relative to other liquid parts.

Bodies expand by its temperature increasing and when increasing its volume density decreases as mass remains unchanged.

If d1 is the new density of the portion considered (d1 < d):

Weight of the liquid portion: p = m. g = V1. d1. g

Thrust acting on the liquid portion: E = V1. d. g

Where V1 is the volume of the liquid portion

These are the called fluids natural convection currents, in which hot parts tend to rise. Natural circulation or thermosyphon systems are based on this phenomenon for supplying hot water by solar collectors.

This content is part of “Solar Energy Introduction” eBook and solar e-learning of Sopelia.

Sorry, this entry is only available in European Spanish.

One of the most important issues in energy conservation areas and solar energy use is undoubtedly homes and workplaces air conditioning application.

This sector accounts about 40% of the total energy consumed. The savings can be achieved by using solar energy for heating is of the order of 60% to 80% depending on house design.

The principles of bioclimatic architecture should be applied in all new urban plans.

When speaking of passive solar architecture, we talk about modeling, selection and use of passive solar technology, which is capable of maintaining a comfortable and pleasant temperature home environment through the sun. This type of architecture is only a small part of the energy efficient buildings design and is considered as part of sustainable design.

There are three types of solar gain:

1) Direct solar gain: refers to the use of windows, skylights and blinds to control the amount of solar radiation reaching the inside of a housing, in combination with mass floors.

2) Indirect solar gain: is achieved through the skin of the building, designed with certain thermal mass. An example of this gain is also the garden roof.

3) Isolated solar gain: is the process in which the main thing is the sun heat passive capture, and then transport it inside or outside the home.

There are considerations to take into account in this type of architecture implementation, to give his best result:

* Building orientation

* Construction features

* Environment use

In existing buildings we can always intervene to improve thermal insulation, sun blinds open in winter or adding a glass gallery on the north side of the house if we are located in the southern hemisphere.

To heat the house with the sun, a clear winter north facade without many neighbors who clog the midday sun is needed.

Main glazings must be on the north facade. For example, if we are located in the southern half of Argentina we need 1.4 to 2 m2 of north glass for every 10 m2 stay we want to heat.

Windows should be closed with curtains or blinds at night to heat captured not escape. It is good to improve thermal insulation as far as possible and have thermal mass (building material in walls, floors) which accumulate the heat of the day to the night. For summer it is necessary to place eaves, awnings, vines, etc. that shade windows in.

You can acces more Spanish language content like this in Manual Técnico – Comercial de Energía Solar Térmica by Sopelia.

What qualities should we consider when selecting a solar thermal collector?

Are two:

1- Its constructive qualities. Determines the durability and architectural integration possibility.

2- His energetic qualities. Determines economic performance.

In some respects both qualities are interrelated.

A good solar collector is one who possesses both qualities well balanced for the intended application.

There is no use a solar collector with an extraordinary energy intake if their constructive qualities fail or degrade quickly, since the profitability of these facilities is measured in the medium term.

There is no use a solar collector with extraordinary constructive qualities if their energetic qualities fail, because, simply, it is not fulfilling its main task.

By observing the solar collector performance curve, we see that it depends on a variable which is the temperature T, which in turn depends on the solar radiation I, on solar collector fluid inlet temperature Te and on ambient temperature Ta.

That is, the performance of a collector depends:

– On one side of the weather conditions, given by I and Ta,

– On the other side of the working conditions, that is, of what it is used, given by Te.

Therefore, when selecting a collector must be considered:

1) The application will have (only ACS, only heating, hot water and heating, pool heating, etc.).

2) Climatic and radiation conditions of facility location.

3) Models performance curves.

4) Equipment price.

5) The economic profitability (based purely on the relationship between price and yield) and investment recovery period.

6) Its construction quality.

You need to balance construction quality with energetic quality.

There is an open debate among professionals about which of the two most used collectors technologies is the most appropriate: flat or vacuum tube collector?

Those who opt for vacuum tube collectors consider them more advanced and argue that in the future this technology will eventually displace definitely flat plate collectors because of their better performance.

The increased cost gap of vacuum tube collectors respect to flat collectors has been reduced and we can find collectors of both technologies at the same price.

Supporters of the vacuum tube collectors consider opting for them is compensated, because by offering higher performance per m2 we will need to purchase less collectors.

This is not necessarily true, especially in small facilities:

In a small facility that only provides ACS with good weather and radiation conditions, flat plate collectors performance and profitability will be greater.

As you increase the size of the installation, the vacuum tube collector highest performance will offset the lower absorbing surface.

We will also consider building integration of vacuum tubes direct flow collectors (U-Pipe) that can be placed vertically covering a façade or balcony.

In short, a properly trained professional must assess based on the following factors choosing one or the other technology:

• Specific requirements of the installation

• Location climatology in every season

• Previous experience

• Budget availability.

You can find content like this in the Technical – Commercial Solar Thermal Energy Manual by Sopelia