The energy self-sufficient family home of the future

Transcription

1 The energy self-sufficient family home of the future Fluctuating energy levels, as is often the case with power obtained through photovoltaics (PV), result in only a partial correlation between generation and consumption. When the energy demand of a household is more or less equal to the PV system yield, independent studies estimate that an average private consumption figure of 30% is achieved. To boost this proportion by any significant amount requires energy storage technologies. Using the energy concept we have outlined here, a figure of 100% is achievable. As a result, complete self-sufficiency in electricity and heat for the home is now a genuine prospect for the future. The concept is being put to the test for the very first time at a Fronius site in Austria. The challenge In principle, renewable energy can be stored at many different levels. Central concepts are being explored in European circles, focussing mainly on large offshore wind farms in the north spreading to central PV systems in the south and large pumped storage electrical power stations in regions such as the Alps. [European Commission (2010), Energy infrastructure priorities for 2020 and beyond]. Such proposals are proving to be quite controversial, as delivery would require intensive long-distance distribution grids extending right across Europe, with a major investment in land and funding. The alternative is local, decentralised storage. The Fronius Energy Cell subscribes to this decentralised approach and generates energy right at the point of consumption - the family home. Furthermore, the waste heat generated can be harnessed directly for hot water and heating purposes, thus achieving an extremely high level of overall efficiency. Central power plants often have no local use for waste heat and district-heating distribution systems are rarely established on cost and consumer infrastructure grounds. The solution During days with sufficient insolation levels, electricity consumers can be run directly off the inverter. Surplus power can be used in several ways. For example, batteries can be charged so that they then provide energy during the evening and night hours (short-term storage) and surplus power generated during the summer months is used to power an electrolyser in the Fronius Energy Cell. Electrolysers produce hydrogen, which is stored in an external tank. In winter, the stored hydrogen is converted back to electricity using the Fronius Energy Cell's fuel cell function (long-term storage). This conversion process in the Fronius Energy Cell also produces waste heat that can be used to provide hot water and heating back-up. The energy management system ensures optimum use and distribution of energy within the entire system. This makes the Fronius house of the future fully energyindependent; all the required energy is generated from photovoltaics and is available at any time. 11/2012 1/6

2 Fig. 1: Fronius Energy Cells concept The implementation This concept was first brought to life at a Fronius site in Austria on the basis of a model installation. The following assumptions were made: / Central European household comprising 4 people. / Connection to the public mains network. / Heated living area: 170 m². / Electrical energy requirement (without heat pump): 3,000 kwh/a energy-efficient household. / Heating requirement: 2,500 kwh/a; 15 kwh/(m² a), lowest-energy house according to the EU Buildings Directive. / Hot water requirement: 1,500 kwh/a (25 litres per person per day). / PV energy generated: 6,000 kwh/a; based on a PV system covering approx. 60 m². / User behaviour and energy flows: The starting point for a breakdown of PV generated energy is ⅓ used immediately, ⅓ after short-term storage and ⅓ after long-term storage. The compact system can be installed in a services room (approx. 11m²) and a hydrogen tank room (7.4m²). 11/2012 2/6

3 Fig. 2: Floor plan A 10 kwh capacity is sufficient for the short-term energy storage needs. Both lead and lithium batteries are used in order to obtain comparative values for the two technologies. Long-term energy storage is provided by using the Fronius Energy Cell as an energy converter and a hydrogen tank capable of storing 1,200 kwh. The tank is constructed in the form of four bundles comprising twelve 50 litre steel cylinders each at a pressure of approx. 200 bar. This storage medium represents state-of-the-art technology and has been harnessed in industrial applications for decades. The key technical data of the Fronius Energy Cell: / Overall efficiency including utilisation of waste heat: > 80%. / Waste heat level: up to 80 C. / By utilising the waste heat from the energy cell, over 2/3 of the annual hot water requirement can be met. Combining the two storage technologies enables important synergies to be pooled. Short-term energy storage takes advantage of the good electrical efficiency offered by batteries, as well as their ability to provide peak power. Storing comparatively high levels of concentrated energy over extended periods of time before delivering this energy in the form of electricity and heat is a particular strength of hydrogen. Further components include the heat buffer store and the water treatment system for generating de-ionised water for electrolysis. Both pieces of equipment utilise the waste heat generated by the Fronius Energy Cell. The inverter links the PV generator, the AC mains network and the storage units. 11/2012 3/6

4 The energy management system Optimum energy efficiency within a building is impossible without a means of simultaneous control over all internal energy flows. These are directed to every point in the house where they are needed. Based on the EY-Modulo system from Basle-based Sauter AG, the energy management system (EM) meets these demands by operating independently across all aspects of the installation to monitor both thermal and electrical requirements within the house in order that energy may be provided on the basis of need. Using this control strategy to optimise private consumption of the solar yield contributes toward the aim of improving self-sufficiency in the home. The prospect of coupling the energy manager to an intelligent grid of the future makes other applications, such as decentralised energy storage systems controlled by the power company in order to reduce variations in grid load, or even private electricity exchanges, a distinct and tangible possibility. Fig. 3: Energy management and energy flows The central command variable for controlling the electrical energy flows within the home is the bi-directional meter on the public grid (Smart Meter). This detects load changes in the house in real time and instructs the EM to trigger the short-term or long-term store to cover the additional demand. The same applies for excess solar capacity: in this instance, the EM considers the continuity of the solar yield to decide what priority it should assign to charging the energy store so that, once the store is full, it can begin feeding energy into the grid. Sanitary and hot water management in the home involves a different approach. Not all thermal needs in the house can be met through waste heat from the Fronius Energy Cell alone. An additional heat generator is therefore integrated into the Sauter energy management system as part of an additional project step. If a heat pump is installed, the EM uses the sum of all recorded temperature and consumption data to determine the optimum supply temperature and necessary flow rate before communicating this data to the pump. Incorporating pellet cookers or even hydrogen water heaters is also envisaged and requires merely that switching signals are transmitted to the devices. 11/2012 4/6

5 The efficient internal control of both energy flows is therefore based on comprehensive and cross-system communication between sensors and actuators. It is for this reason that the Sauter energy management system has been largely equipped with upgrade-compatible interfaces such as Powerline and RF. A LAN interface to the web server enhances both the wireless and hard-wired visualisation of all internal user data. An additional cloud server grants external access to the data and also enables remote maintenance. Should the need arise for a load management system as well, even older consumers will have no problem connecting such a system using a socket adapter. Conclusion This concept demonstrates the efficiency of PV. Electricity and heat independence is possible throughout the year by using decentralised PV. Reducing system costs is the challenge that must now be overcome to open up the residential market. Standalone systems can form the basis for establishing an early market presence. Governmental policy and energy pricing developments will be significant factors influencing market establishment. Characters (with spaces): 1,382 Words: 7,427 Michael Schubert, Sales Development Solar Electronics, Fronius International GmbH. (Copyright to photos: Fronius International GmbH, reproduction free of charge.) Dr. Thomas Laux, Manager OEM Sauter Group, Sauter AG in Basle (Copyright to photos: Fr. Sauter AG, reproduction free of charge.) 11/2012 5/6

6 About Fronius International GmbH Fronius International GmbH is an Austrian company with headquarters in Pettenbach and other sites in Wels, Thalheim and Sattledt. With 3,250 employees worldwide, the company is active in the fields of battery charging systems, welding technology and solar electronics. Around 95% of its products are exported through 17 international Fronius subsidiaries and sales partners/representatives in over 60 countries. In financial year 2010, the company generated a total turnover of 499 million euros. With its outstanding products and services and 737 active patents, Fronius is world technology leader. 392 employees work in research and development. About Sauter AG (Basle) The Swiss-based SAUTER Group is considered in many parts of the world to be one of the leading technology companies in the fields of building automation and system integration. As a specialist, SAUTER develops, manufactures and distributes energy-efficient solutions for building management systems. The company's project portfolio includes well-known references for the following types of property: offices and administrative buildings, research and educational institutions, hospitals, industrial and laboratory premises, airports, leisure complexes and hotels. The company's four divisions Systems, Components, Services and FM provide holistic expertise in building management: SAUTER creates environments for the future. Enquiries: Author: Dipl.-Ing. Michael Schubert, , schubert.michael@fronius.com, Froniusplatz 1, 4600 Wels, Austria. Dr.-Ing. Thomas Laux, , thomas.laux@ch.sauter-bc.com, Im Surinam 55, 4016, Basle, Switzerland. Technical press: Mag. Andrea Schartner, , schartner.andrea@fronius.com, Froniusplatz 1, 4600 Wels, Austria. Dorothée Kössler, , dorothee.koessler@ch.sauter-bc.com, Im Surinam 55, 4016 Basle, Switzerland. 11/2012 6/6