2021 And The Fable Of Solar Self-Consumption

Previous clarification: we are in favor of renewable energy in general and solar energy in particular. We dedicate ourselves to that.

This does not prevent us from taking a critical look at how the sector is developing.

Making the parallel with a famous rear, on the one hand we have “the resistance” (individuals and companies) and on the other, “the dark side” (public administrations and energy trading companies).

The discourse is that renewable energies, in addition to helping us combat climate change, will provide us with energy independence.

Our territory is full of solar and wind farms and more and more photovoltaic systems are being observed on the roofs.

But the reality is that energy price in some countries has increased almost fivefold in the last 2 years and that solar self-consumption benefits, in most countries and mainly in residential sector, vanish in tolls and unclear compensation systems.

In case of large-scale renewable systems, coupling energy generated with distribution network is still inefficient. To assess its location, in most cases scientific, technical, ecological, economic and social criteria have not been used to minimize its impact on the landscape, biodiversity and the way of life of the inhabitants of the affected territories.

As for solar self-consumption systems, currently they are only interesting in those activities in which solar radiation hours coincide with energy consumption hours.

Making the parallel with another well-known rear, to overcome these obstacles we must find the holy grail as soon as possible: an efficient and cheap energy storage system.

Meanwhile “the dark side” continues to beat “the resistance” by a landslide. One of its members regulates the sector with regulations and procedures for setting rates tailored to the interests of the other, and the other member is a voracious tax collection agent for the former.

We have other bad news … doing things right way is against the interests of “the dark side.”

How should things be done? Relying on 3 basic pillars:

1) Energy efficiency

Making more efficient use of available resources runs counter to the established idea that increasing GDP is synonymous with progress. It would involve manufacturing more energy efficient devices and reducing their planned obsolescence. In short, use fewer resources and generate less waste. Or what is the same, give priority to the environmental quality over the economic quantity.

El momento de la eficiencia energética? | Blog IL3 - UB

2) Renewable energies

Of the 3 pillars, it is the only one in which there is consensus and in which the most progress has been made. The replacement of fossil resources that produce the greenhouse effect with renewable resources for power generation is practically out of question.

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3) Distributed generation

Here, too, the clash of interests occurs. Distributed generation is synonymous with energy independence and this does not interest the “dark side”. It would imply less control, fewer tolls, transparent or zero compensation systems, and less tax collection.

Distributed generation entails decentralization in interconnected generation cells and consequently the minimization of losses caused by energy transport. Power generation is close to consumption points, favoring self-consumption. This translates into energy savings, cost reduction and energy system transparency.

Using sites in urban and industrial areas (roofs) close to consumption points would have a lower impact on biodiversity.

The opposite of centralization and control. With a centralized energy network like the current one, energy is generated in plants located at great distances from consumption places. This requires a complex transportation and distribution infrastructure. From an economic point of view it represents a high profitability for its operators, but it entails a high environmental impact and a high performance loss (close to 20%); motivated by the transformation processes necessary to transport electricity.

La ULE dedica un curso a la generación distribuida y fotovoltaica

Is important the contribution of small-scale solar thermal energy with a performance twice that of photovoltaic solar energy.

Many countries, such as Spain, have incorporated it as an essential requirement for obtaining a building license for any new building.

This is very positive, but unfortunately we can affirm that approximately 4 out of 10 of these facilities do not work properly because the inspection is limited to obtaining the building license and not to its operation and subsequent maintenance; as in the case for example of a gas boiler.

Both “the resistance” and “the dark side” know that this is the way.

But the first is scattered and only has the strength to rise from time to time a few ephemeral media characters and the second continues to pull the strings in the shadows with the sole objective of maximizing its benefits.

From time to time they meet to take a photo and issue empty statements of intention of concrete objectives and plans and assign million-dollar budget items that one knows where they will go. The last one was in Rome last October.

From Sopelia we encourage you to join “the resistance” and to continue fighting against climate change, each one in his field and in his day to day because as a friend of ours says: there is no planet B.

All you need is Sun. All you need is Sopelia.

Solar Energy Paraguay

Paraguay has one of the highest proportions of renewable energy in South America. Hydropower constitutes around 99.5% of the installed electricity capacity. This makes it highly dependent on the rivers that feed the country’s main hydroelectric plants, from where most of the electricity produced is exported to neighboring countries.

By 2020, renewable energies had reached an installed capacity of 8,832 megawatts (MW). The hydroelectric capacity represented 8,810 MW (47% of its energy supply). In second place, there is biomass (33%), most of which is unsustainably exploited, and lastly, hydrocarbons (20%), all imported.

Paraguay holds the rare title of the world’s largest exporter of electrical energy, but many argue that it is an inefficient exporter because the compensation it obtains is much lower than the market price of energy; at the same time as an inefficient consumer because it uses a very low amount of its installed hydroelectric capacity.

From the perspective of energy demand, the main energy source is biomass (44%), followed by hydrocarbons (40%) and, in a distant third place, electricity (16%). The main source of energy produced in Paraguay is thus the least used in the country.

Paraguay has ratified the Paris Agreement in 2016, the 2017 National Climate Change Law, and the Nationally Determined Contribution, updated under the Paris Agreement and presented in July 2021.

Qué es la energía solar térmica y para qué sirve?

The Atlas of the solar and wind energy potential of Paraguay is one of the tools developed by Itaipu to make visible data of great relevance for developers of these technologies interested in new generation projects in this country.

That document reflects a promising future for solar technology.

Regarding the solar energy potential, it is represented in average daily solar energy accumulated in one year per surface unit (kWh / m²-year). This map denotes considerable potential throughout the territory, with a positive trend towards the north of the country, registering maximum figures that are between 1850 and 2000 kWh / m²-year, especially between the departments of Alto Paraguay, Boquerón, Concepción, Amambay, San Pedro, Canindeyú and Alto Paraná.

Non-Conventional Renewable Energies such as wind and solar still have very low percentages in the installed energy matrix. For this reason, the Vice Ministry of Mines and Energy of Paraguay (VMME), the Itaipú Binacional, the Itaipú Technological Park (PTI-PY), the National Electricity Administration (ANDE) and other entities, would be drawing up a strategic plan to promote these alternative energies.

Currently, Law 3009 of 2016 is in force. Calls for bids were made within the framework of that law but no awards were made, because at the time projects prices were not better than those of Itaipu.

In addition, they required a self-generation license and sales to third parties were prevented.

With the changes introduced to regulations that regulate the sector, solar is expected to be the most competitive non-conventional renewable technology in 2021.

You could have a solar MW at 39 dollars, while for hydroelectric it would be USD 47 and for wind USD 43.

Diario HOY | ¿Aire, heladeras y otros aparatos movidos a energía solar?: Costos, pros y contras

Every day, thousands of people, mainly in Asunción and the Metropolitan Area, are left without electricity for several hours.

This problem has forced us to consider the need to look for other alternatives that help compensate for the lack of good service and, in turn, face constant power outages.

The use of solar energy, although it is not yet very popular in Paraguay, could be a solution.

All you need is Sun. All you need is Sopelia.

Financing and Sale of Green Projects

Sopelia provides support for financing and sale of green projects around the world.

The documentation to provide to access this financing must include:

1) Country in which the project is located

2) Type of project

3) Power in MW

4) Permissions you already have

5) PPA (if you already have it or if you are in the process of obtaining it)

6) Environmental study

7) Legal study

8) Social impact assessment

9) Property or land rights

10) Study and interconnection zone.

This information is analyzed by Sopelia and sent to the investment funds with which the company operates for evaluation.

Those funds interested in financing the project will sign a letter of intent with the project owner before signing the final contract.

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Regarding projects sale, the documentation to be provided must include:

1) Corporate structure of the owner

2) IT code

3) Installed capacity in MW

4) Historical production of last 4 years

5) Value of tangible and intangible fixed assets and depreciation schedule

6) Existing balance in accounts (operational, CRSD and maintenance)

7) Detail of annual operating costs (indicating scope and term of the O&M contract)

8) Financing contract (calendar, pending debt, Swap, type, margin, annual agency cost)

9) Equity structure (participating loans, value and annual cost)

10) Tax credits (BINS, financial interest to be deducted, environmental credits, tax credits for amortization limitation, etc.).

This information is analyzed by Sopelia and sent to the investment funds with which the company operates for evaluation.

Those funds interested in acquiring the project will sign a letter of intent with the project owner before signing the final contract.

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Both in financing and in projects sale, it is a sine quanon condition to provide all the detailed information with its corresponding supporting documentation.

To understand financing process for these projects, you can access the following posts:

Green Projects Financing

Green Projects Financing(II)

All you need is Sun. All you need is Sopelia.

ISOLATED PV SOLAR SYSTEMS DIMENSIONING

Isolated PV systems do not need a connection to an electrical network and their operation is independent or autonomous from said network.

Applications that are currently being implemented the most are small installations for lighting houses that are not reached by the general network, pumping, various agricultural facilities, signaling, hostels, campsites, shelters, summer and weekend chalets.

The criterion followed in isolated PV systems sizing is not so much to produce maximum energy but rather the concept of reliability appears (to ensure the proper functioning of the system, ensuring that failures are minimal).

Sizing an isolated photovoltaic system requires 7 steps:

1. Estimation of electrical load (electrical consumption)

We must know power of each element of consumption and the estimated time of use. Normally the calculation is made using W / h as the unit of energy.

To estimate these values we can consult following link

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2. Estimation of solar energy available

Hm is the energy in kWh that affects a square meter of horizontal surface on an average day of month m. From the corresponding table the value is obtained in MJ / m2 (mega joules / m2).

The conversion must be carried out and expressed in Wh / m2 or kWh / m2. Being 1 MJ at 277.77 Wh or 0.277 kWh.

To estimate these values we can consult following link

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3. Battery sizing

To define accumulator size, you must set N (Days of autonomy). It is the number of consecutive days that in the absence of Sun, accumulation system is able to meet consumption, without exceeding maximum discharge depth of the battery.

Having identified N and knowing the total energy required Et (final electricity consumption) in a period of 24 hours, we are going to calculate the real energy Er that the modules must contribute to the chosen battery (which will have a maximum admissible discharge depth pd).

The daily energy Er must take into account the different losses that exist:

Er = Et / R

Where R is a global factor of installation performance, whose value will be:

R = 1 – [(1-kb-kc-kv) ka. N / pd] – kb – kc – kv

kb: coefficient of battery performance. It varies between 0.05 (if there are no intense discharges) and 0.1 (for more unfavorable cases).
ka: self-discharge coefficient. If the data does not appear on the battery’s technical sheet, it can be estimated at 0.005 (0.5% daily).
kc: loss coefficient in the converter. If the system does not incorporate an inverter, it is zero. It ranges from 0.2 for sine wave inverters to 0.1 for square wave inverters.
kv: coefficient of other losses. It is usually estimated at 0.15 and 0.05 if we have already considered the performance of each device when calculating consumption.

Once R is calculated and Er obtained, we proceed to determine the useful capacity Cu of the battery. The battery must be able to accumulate the energy to be supplied throughout this period:

Cu = Er. N

To go from Wh to Ah, we will divide Cu by the nominal battery voltage (usually 12 V or 24 V).

Now we calculate the maximum nominal capacity C assigned by the battery manufacturer. These capacities will be assigned for temperatures between 20º and 25º C.

C = Cu / pd

With these data, the batteries offered on the market will be selected that most closely approximates the nominal capacity C obtained.

To estimate these values we can consult following link

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4. Dimensioning of modules area

Energy originating in modules that must reach the accumulator (Er) suffers losses originated by the regulator, which are estimated at approximately 10%; therefore the daily amount of energy to be produced by the Ep modules is:

Ep = Er / 0.9

From the following formula we will calculate the HSP (hours of peak sun or hours of sun at an intensity of 1000 W / m2), starting from H expressed in MJ (1 kWh = 3.6 MJ):

HSP = 1 / 3.6k. H (MJ) = 0.2778 k. H

k is the correction factor for modules inclination according to the latitude of installation location.
H is the average daily radiation of each month expressed in MJ / m2.

To access these values we can consult following link

As we have already said, we must base ourselves on the most unfavorable month and also correct according to area climatological factors (clean atmosphere or mountain area = 1.05; area with pollution = 0.95; area with fog = 0, 92).

The ideal orientation is always towards equator and to determine the inclination we can follow recommendations in PV modules support structure post.

To calculate modules number we will use the following formula:

NM = Ep / 0.9. Pp. HSP

Pp is nominal (peak) power of chosen modules. The most suitable modules combination for the installation will be selected (price, available space, load to satisfy, etc.).

It is multiplied by 0.9 to consider possible additional losses that can cause modules dirt, reflection, etc.

If result is not a whole number, it will be rounded to the higher unit if decimal is equal to or greater than 0.5 and lower if it is less than 0.5.

Knowing the total modules number of PV generator and battery nominal voltage, which coincides with installation nominal voltage, it is possible to determine if it is necessary to group the modules in series and in parallel. The number of modules to be connected in series is calculated as follows:

Ns = VBat / Vm

Where:
Ns modules number in series per branch
VBat nominal battery voltage (V)
Vm nominal voltage of the modules (V)

And the number of branches in parallel to connect to supply the necessary power is given by:

Np = NM / Ns

Where Np is the number of modules to be connected in parallel branches.

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5. Specify the controller or regulator

For sizing we can consult Solar charge controller post.

The installation will be dimensioned in such a way that the safety factor corresponds to a minimum of 10% between maximum power produced and that of regulator. The minimum possible number of regulators will be used.

To find the number of regulators Nr we will use the following equation:

Nr = Npp. ip / go

Being:
Npp the number of modules in parallel.
ip the peak intensity of the selected module.
go the maximum intensity that the regulator is capable of dissipating.

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6. Sizing of the inverter

When sizing the inverter, the power demanded by the load made up of AC devices will be taken into account, so that an inverter will be chosen whose nominal power is slightly higher than the maximum demanded by the load.

For inverter sizing if PV systems has AC devices we can consult Solar converter post.

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7. Choice of cable section

To select the cable section, the recommendations in the section Other elements (Wiring) post will be taken into account.

The sizing of the wiring constitutes one of the tasks in which special attention must be paid, since whenever there is consumption there will be losses due to voltage drops in the cables.

We can consult Solar wiring post.

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This is an extract of contents included in Technical-Commercial Photovoltaic Solar Energy Manual and Sopelia e-learning training.

All you need is Sun. All you need is Sopelia.

Solar Thermal Insulation

Thermal insulators are essentially characterized by their thermal resistance and thermal inertia.

Thermal resistance is defined as difficulty that a product of a given thickness presents in allowing heat to pass under unit surface conditions, temperature difference and time. By definition, it is ratio of thickness to thermal conductivity.

Thermal inertia is physical ability of a material to maintain its temperature.

The best insulators are air, polyurethane foam, fiberglass, cork (expanded), glass foam, wood fiber sheeting, sponge rubber, PVC, expanded vermiculite, sawdust, loose vermiculite, and linoleum.

Thermal insulation primarily represents economy, because by preventing heta transmission, passage of energy from one body to another is avoided. In addition, thermal insulation represents an investment that will be recovered in a relatively short time, with energy savings that will be obtained, and with best efficiency and operation of equipment and machinery.

If solar thermal system is not thermally insulated there will be a loss of heat and to counteract this phenomenon system will have to resort to auxiliary energy to be able to maintain the required temperature. Therefore, if the system is thermally isolated, heat loss will be avoided and solar energy will be used, preventing auxiliary energy equipment from being activated.

Thermal insulation will also represent protection for personnel who may be in accidental contact with hot surfaces.

Resultado de imagen de aislamiento solar térmico

Characteristics of a good insulator:

1. Low heat conductivity.
2. Lightweight (do not burden system weight)
3. Fireproof and rot resistant
4. That it is not attacked by rodents or insects and that it does not breed insects
5. Inert
6. Easy to place.

Places where insulation is most relevant are: collectors back, pipes and accumulator.

As a reference, minimum insulation thickness of interior pipes is set in Spain by the RITE (Regulation of Thermal Installations of Buildings), as indicated in the following table:

Resultado de imagen de grosor mínimo del aislamiento de las tuberías interiores está fijado en España por el RITE

For materials with a thermal conductivity other than 0.04 W / m ºC, thickness will be determined by multiplying table value by λ and dividing by 0.04.

For pipes sections installed outside, minimum thickness indicated in the previous table must be increased by 10 mm.

The insulating material shall be secured with suitable means, so that it cannot detach from the pipes or fittings.

Insulation will not leave visible areas of pipes or accessories, leaving only the elements that are necessary for proper functioning and operation of components to the outside.

For protection of outdoor insulating material, a plaster cover or coating protected with asphalt paints, fiberglass reinforced polyesters or aluminum sheet may be used. In case of tanks or heat exchangers located outdoors, plastic fabric linings may be used.

Special care must be taken to guarantee pipes insulation durability, especially in outdoor sections exposed to sun, which must have the following insulation characteristics:

• Inalterability due to atmospheric agents and resistance to fungi formation.
• Resistance to solar radiation; otherwise, it must be adequately covered with protective covers or paints.
• Sealing of passages to outside and elimination of thermal bridges.

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

All you need is Sun. All you need is Sopelia.