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Solar energy 24/7.Solutions for maximum self-consumption of solar power in residential areas.

PREVIEW

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How can fuel costs and dependency on energy supplies in residential areas be minimised or even eliminated? KACO new energy provides the answers in this brochure.

The key lies in renewable energy supplies from solar en-ergy and the creation of an energy balance for a whole group of buildings. By means of an integrated approach to the generation and consumption of electrical energy, an aggregate effect arises which results in smoother, im-proved, overall consumption.

The cost of producing electricity from photovoltaic sys-tems is competitive with conventional power stations all over the world. It therefore makes most sense to use one´s own solar power. Such a de-central energy provision sup-ply reduces energy transportation losses and the need for

Introduction.balancing mechanisms at a higher grid level. Bundling to-gether additional technology in residential areas, mainly storage technology, creates additional savings on invest-ment and running costs.

Systems with different characteristics will be needed to generate and store energy. In order to meet the require-ment for minimum costs, a variety of energy technologies can be combined to form hybrid systems.

The energy concept provided by KACO new energy con-sists of three pillars: renewable energy generation, ener-gy storage and distribution via the power grid. Above all else, control units assume the demanding task of energy management. At any given time they have to intelligently link information relating to energy generation and energy

storage management, thus assuring uninterrupted ener-gy provision to the residential area. Power generators and energy consumers are consequently combined into one functional unit thanks to a uniform communication stand-ard which can cope with the temporal balance of energy supply and demand.

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KACO new energy’s scope of services includes the acqui-sition of components and planning for PV generation and distribution, electrical storage and the electrical and over-all energy management. Thermal support (right) of the energy concept is optional and will be implemented by specialized partners.

Energy concept. It all starts with the rising sun.

In KACO new energy you have found the right partner when it comes to building a high-performance photovol-taic system. As a pioneer in the branch, our core-com-petence lies in the development of solar inverters, which indeed represent PV system intelligence.

In 1999 KACO new energy became a leader in this tech-nology following the launch of the first serially-produced, transformerless inverter, which was capable of achieving higher rates of efficiency.

Nowadays, KACO new energy is one of the largest global-ly-operating manufacturers of inverters in each and every performance class. That means that you can build central-ly-designed solar power plants right into the megawatt range using just a few central inverters, or you can achieve the same result in a de-centrally designed plant using nu-merous inverters of a lower performance class. Custom-ers also appreciate the comprehensive technical features included in the standard ex-works delivery scope of the inverters. These include:

a clear graphic display depicting all current operating details,

the numerous interfaces, such as USB and Ethernet, for continuous communication,

the data logger complete with web server for remote monitoring and data storage,

the string collector with string fuses and surge protection.

Pre-set country settings facilitate simple commissioning all over the world. The appropriate settings may be selected from the display in just a few clicks. Moreover, the menu navigation is multilingual.

The majority of KACO new energy inverters have been conceived for use outdoors meaning that the units will al-ways be able to stand up to the environmental conditions at the installation site.

We will be very pleased to design a strategy which en-ables you to avoid any unforeseen circumstances which may crop up during installation of this innately mainte-nance-free technology. In the framework of integrated concepts for residential areas we will also supply the solar modules together with the inverters from a single source.

As part of a renewable energy concept for residential ar-eas, our inverters feed the energy from the modules into the internal power grid. First and foremost, the solar ener-gy is used to cover momentary energy requirements. Once these have been covered, the surplus energy flows into the central battery storage system, from which it can later be released for demand-driven supply of consumer loads. If required, the inverters also control the feed-in of addi-tional solar energy into the grid.

ElectricalEMS

PV module PV inverter

Man

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ent

Batterystorage

Batteryinverter

Storage

Gen

eration

ThermalEMS

GasCHP

Heatpump

Gas peak load boiler

Thermalbuffertank

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Storage

Gen

eration

Overall EMS

Washing machine

Lighting

DishwasherAir conditioning

Electric carThermal heat

Emmersion heater

Measuring point Measuring point

Con-sumptionmeter

Consumptionmeter

Publicgas grid

Publicgrid

Cooker

Water

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Used together in a concept with storage systems, self-con-sumption of solar power can be increased considerably because it temporally uncouples power generation from consumption. If surplus electricity arises during daylight hours because of high solar irradiation this can be used to charge batteries. Solar energy thus also contributes to covering electricity demands even at times when sufficient power would not otherwise be made available because of bad weather or during darkness.

However, a storage concept does not just stop at solar power storage. If the PV system is generously dimen-sioned, surplus energy can be used for operating ther-mal storage systems. It is therefore possible to increase self-consumption, even reaching energy autarky, by using solar energy to provide heat and hot water.

If there is a connection to the public grid, a solar resi-dential area fulfils additional purposes. Surplus electricity can of course be fed into the grid. On the other hand, a high proportion of self-consumption reduces the load on the grid eliminating grid infrastructure costs. In the frame-work of wider concepts, such residential areas could be used to assist grid management when batteries release stored electricity into the grid or absorb electricity from the grid in the event of grid problems.

AC-coupled, bidirectional battery inverters function as electricity distribution drivers in that they charge and dis-charge central batteries. Because of their high rate of effi-ciency and split-second reaction times, KACO new energy battery inverters guarantee uninterrupted power supply to the homes. The battery inverters are very compactly designed and consequently do not pose any special logis-tical challenges. They are furthermore based on the same platform as our solar inverters, profiting therefore from the same type of assembly and operation.

The flexible battery interfaces ensure compatibility with all standard batteries ranging from lead to lithium. In consul-tation with you, we will also take care of purchasing the batteries which meet your requirements.

Once the components for PV generation and storage have been established, we can also provide services such as planning, how to set the parameters of the products, and how to connect the components to each other to achieve the best interactive results.

When the setting sun does not mean the end of solar energy provision.

Complete energy management for solar energy around the clock.

The use of solar energy is organised via a central control unit. By comparing the momentary need with long-term patterns of use, the energy management system achieves the ideal balance between immediate use and storage – that means nothing more than maximum self-consump-tion. A complete measuring and monitoring system re-cords all energy flows. Regular analysis of this data means that energy management can be optimised continuously. The energy concept completely depends on complex con-trol algorithms which take care of optimum interaction between all generators and consumer loads. This is the only way to ensure that supply can be guaranteed at all times and that economic and ecologic use of solar energy can be achieved. To this end, KACO new energy uses an innovative, modular IT structure, by which means inter-connected components can exchange information with one another. A complete, high-definition data map of all energy flows in the project results from this, which then forms the basis for the development of intelligent control algorithms.

The electrical energy management system (EEMS) controls the electrical energy concept whereas a separate thermal energy management system (TEMS) would implement the thermal energy concept. The higher-level overall energy management system (OEMS) comes into play to:

form the interface to the EEMS and the TEMS connect the EEMS and TEMS to one another enable commands from the public grid to be integrated.

Covering acute energy requirements always carries the highest priority. Once this has been covered, surplus solar energy will be used to charge the electrical batteries. Only when these have been charged, and electricity is still avail-able, will the OEMS enquire about thermal usage or it will stipulate feed-in to the public grid.

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23 households, 145 kW installed solar power, one cen-tral electrical storage system and multiple thermal storage systems: in the German town of Weinsberg, KACO new energy has realised a pilot project that shows how it is possible to completely meet energy requirements with so-lar power.

Owners of photovoltaic systems, whether private or com-mercial, typically only cover a small portion of their elec-tricity requirements with self-generated solar energy. In the past, it was standard practice to sell back one’s solar power to the regional power grid operator – promoted by Germany’s Renewable Energies Act. The power drawn from the grid for household consumption also remained standardised. Of course, these relationships originated during a time when the feed-in tariff (FIT) was significantly higher than the costs for consuming electricity from the grid. Since the FIT for newly installed PV systems has sunk to a level much lower than the private consumer price per kilowatt hour, the situation is now worth reconsid-ering. In light of the rapidly sinking cost of investment in a photovoltaic system – resulting in acquisition costs of about 10 euro cents per kilowatt hour in Germany – it be-comes quite clear how solar power is used most sensibly: consumed directly on-site and, in fact, not only used for electrification but also for heating and hot water supply. Touching on this has been a taboo in a typical discussion about environmental issues, because it is synonymous with ‘wasting energy’. But only if the focus is on “fossil fuel energy” and “power line losses”. If the electricity is derived from local photovoltaic systems, it is considered to be an economically and ecologically perfect source of heat energy.

Self-consumption needs management The concept may seem logical and simple, but the tech-nical implementation requires a great amount of know-how from all building trades involved – and of course a scale sufficient to convince doubters and enthuse interest-ed parties. Thus, KACO new energy GmbH joined forces with a “seasoned” solar builder and the experts at the Fraunhofer ISE (Institute for Solar Energy Systems) to deliv-er proof of complete renewable energy supply for a new-ly built housing estate. On the outskirts of Weinsberg in the German state of Baden Wuerttemberg, six detached homes, three town houses and two larger, multiple-flat family residences were built. The “power plants” generate an output of 145 kilowatts of photovoltaic electricity from an installation on the roofs of the buildings. As one goal of the project was to provide the “greatest possible de-gree of electrical independence”, the photovoltaic gener-ator was slightly over-dimensioned and maximum use was made of the roof area for installing PV modules. KACO new energy, responsible for providing energy to the hous-

ing estate, approached this with an integrated concept that achieved a high degree of coverage with solar power and consequently the lowest possible feeding in of solar power into the grid: Excess electrical energy coming from the photovoltaic generator which is not needed at that moment is transferred as electricity into an electrochemi-cal storage system, as well as to a thermal storage system for use at a later time.

An AC-coupled bidirectional battery inverter, which charges and draws electricity from the lithium-ion bat-teries, serves as the central unit of the electrical power distribution. The batteries – with a capacity of 150 kWh – serve as a buffer for solar power that is not immediately consumed. Due to its degree of efficiency, and particular-ly it having the shortest response times, the bidirectional battery inverter ensures that the power supply to a house-hold is uninterrupted, including stable off-grid operation of the entire dwelling in the event that the public distri-bution grid fails. Solar power which is not immediately in demand by electrical consumers drives a heat pump with 35 kWel output, which in turn feeds a buffer storage unit with a 20 000 litre capacity. It only serves the heating sys-tem, and is therefore completely separate from the drink-ing water system. In addition, 18 smaller de-centralised water tanks are heated directly; they are located at the in-dividual buildings to cover the daily demand for hot water. An energy management system was created for the entire residential complex, which assumes control of all electrical and thermal components. Through the perfect reconcilia-tion of current needs and long-term usage patterns, this energy management system achieves the ideal balance between direct consumption and both the “battery” and “water compartment” storage technologies. This means nothing less than total coverage of the complex self-con-sumption. A comprehensive measuring and monitoring system records all of the housing estate’s electrical and thermal energy flows. The regular analysis of this data ensures that the energy management is continually op-timised.

Ready for anything Not only is the housing estate integrated in the usual public electricity grid but also in a local heating network, which is connected to all buildings. If, due to the weath-er or consumption, the electric power supply from the photovoltaic system and storage system is insufficient for the heater, an integrated combined heat and power unit (CHP) with 11 kW electrical output and 27 kW thermal output is put into operation. Because the CHP serves as a “backup”, it only makes a minor contribution towards heating the homes and is thus switched on for less than its required economic operating period. For the cold-weath-er season, a natural-gas-operated peak-load condensing boiler with 240 kW output is also available.

Tough learning curve One of the most important lessons to be learned from such a complex system is certainly just how important and arduous it is to integrate both ‘heat’ and ‘electricity’ as-pects together in one single project with one single goal. This is especially the case when both sides – the technical planning and the implementing parties – are actively in-volved and, particularly the latter, have to take on sub-stantially more programming and calibration work for heating than is usually the case with electrical projects. This can lead to “translation errors”; there is an ongoing need for communication in handling the project. As for the status today, it should be noted that similar sys-tems will pose new and very individual challenges to the people responsible for the project; there is no “mould” for casting the most efficient integration of electricity and heat, fed by photovoltaics. A modular software structure for the energy management system (EMS) appears, how-ever, to be an absolute necessity in any case. Particularly in this regard, we acquired a higher level of expertise that bolstered our solid understanding of the subsystems and focus on the potential for reapplying this knowledge in future implementations.

Target and actual values The modelling for the described layout shows that the de-centralised production and storage of solar power plus CHP covers 97% of the electricity demands and around half of the heating demands of the model housing estate. Our simulations show that 100% coverage of heating re-quirements is merely a question of the insulation standard applied. In the actual system, major intervention was nec-essary in order to adjust the interoperation of the com-ponents.

What does the comparison between the forecast for elec-tric power and heat provision and the actual measured values look like? Firstly, it should be pointed out that the specification for 97% of the electricity to be self-generat-

ed stems from the model: The maximum to be expected was at the same time the target value. This was not only ambitious but risky, because there was no leeway for any uncertainties. And they, to be perfectly honest, will come up in any case; the more complex a system, the greater the element of surprise.

The gas consumption to date has been surprising, for example: according to current projections, it will clearly exceed the determined target volume. The conclusive ex-planation comes from the residual moisture in the build-ing structure. Although the dryers had drawn substantial amounts of electricity from the grid, the complete “drying period” is significantly longer than one would generally expect. Indeed, up to two years can pass before the tem-perature and moisture content of an entire building are in line with the ambient environment.

Where we have put theory into practice.

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Elements of the Weinsberg energy concept.

→ Internal AC grid→ PV plants on the rooftops

→ Decentral thermal storage

→ Thermal plant room

→ Power electronics plant room

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Plant rooms.

→ Inverters - Solar PV inverter: direct feed-in

into the AC grid - Bi-directional battery inverter:

charging and discharging of the central battery

→ Central battery bank with 150 kWh lithium-ion batteries

→ 20 000 litres central water tank for thermal buffer storage

→ 240 kW Gas peak load boiler

→ Cogeneration of heat and power via a gas-CHP with 11 kW electrical and 27 kW thermal power

→ Central heat pump with 90 kW thermal power and a connected electrical load of 35 kW

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Summary. Awards.

The purpose of the model project was to show the signifi-cant role that renewable energy can play in a new housing estate. The well thought out combination and control of tried-and-tested components, as well as, the integration of electricity and thermal storage led the mission to suc-cess. The results mean that some of the commonly-be-lieved arguments against renewable energies can be dis-proved.

On the energy side of things, challenges such as de-cen-trality, solar coverage ratios and power-to-heat were the driving forces for the engineers in charge of the project. There is a need to provide intelligent answers to temporal energy surplus and lacks of energy caused by fluctuating renewables energies.

Which expectations did the project fulfil? The creation of a family-friendly residential area and

high-degree integration of a de-central, renewable energy supply.

The highest possible solar coverage ratio for the elec-tricity supply which means that the energy generated is used to a very large extent in the residential area itself.

Intelligent use of electricity and thermal storage units (150 kWh lithium ion batteries for the electrical energy storage unit and a 20 000 litre buffer tank for thermal energy storage).

Use of surplus electricity in summer, late spring and early autumn for heating water and providing some heating by means of a central heat pump (“Power-to-heat”).

Covering electricity and heating deficits in winter from the combined heat and power unit under optimum operating conditions (peak load cover).

Considering all of these findings it becomes clear that: re-newable energy can be used in combination with storage units to cover base loads, whereas easily controllable gas power plants or combined gas heating and power units will take care of peak load capacity. The present project can therefore serve as a model for consistent, de-central, renewable energy supplies to residential areas or indeed on larger scales.

The „Weinsberg model project“ received the first “Smart Grids-Quartier-Award“ in March 2015.

The battery inverter concept was awarded the SEMIKRON Innovation Award 2013 “Innovative Power Electronics for the Next Generation Village Energy Supply“.

www.kaco-newenergy.com