A smart solution

16 homes, 155 apartments and two office buildings: A new residential area is under construction in the Räbmatt area in the town of Küssnacht am Rigi. The buildings have been designed to Minergie standard and are equipped with heat pumps and photovoltaic systems. Elektrizitätswerk Schwyz AG (EWS), which belongs to the Axpo Group, is responsible for the smart energy solution.

The energy future has already begun here: Building design has been certified for Minergie standard to minimise energy losses. The houses are equipped with photovoltaic systems and heat pumps, and heat and water consumption is automatically recorded with smart meters from EWS, a subsidiary of Centralschweizerischen Kraftwerke AG (CKW).

The building contractor for the Räbmatt development at the foot of the Rigi in Küssnacht (SZ) is Vanoli Immo AG represented by Vanoli General Contractors. The company put a special focus on sustainability. The project was launched in 2016. The 16 houses are being constructed in three phases and are scheduled to be completed by 2021. The first buildings were occupied in the winter of 2017.

Environment and budget

The state-of-the-art energy concept for Räbmatt takes the environment and residents' budgets into account - according to the Energy Strategy 2050 - using local producers and renewable energies to the greatest extent possible.

Water from Lake Lucerne is used to produce energy for heating systems and hot water by means of heat pumps. A maximum of 650 cubic metres of water per hour can be taken from the lake - maximum heat extraction is 1,407 kilowatts. The water catchment is about 100 metres off the shore and also supplies a nearby school with water.

New methods for suppling power

The EWS specialists were also able to demonstrate that the housing development offers the optimal prerequisites for the operation of emissions-free, low-maintenance photovoltaic systems. The panels have been installed on roofs at a slight angle and designed with a capacity between 20 and 30 kilowatts depending on energy needs explains Roman Gwerder, Head of Distribution at EWS.

In order to optimally utilise the locally produced solar energy a private consumption community was established for each building (see box). Measurement data indicates how much electricity is being taken from the photovoltaic systems round the clock. Surplus energy is used to produce hot water thanks to an intelligent control system - and if this storage system is full, excess energy is fed into the EWS grid. If more power is being consumed than produced, EWS supplies the required electricity from its own grid.

The first results from the energy management system indicate: The level of self-supply in the houses occupied in 2017 is about 50 to 60 per cent. "That's not bad," says Gwerder. What's more, customers are happy with this state-of-the-art energy supply infrastructure based on feedback received at the first owners and renters meeting.

Transparency for the customer

EWS is also responsible for transparent, consumption-based billing for the procured power. The smart meter reads the data in 15-minute intervals. By means of energy data management this information is processed automatically. Every customer receives a detailed, quarterly statement which includes the proportion of local solar power in relation to total energy consumption. In addition, the smart meter also records heat and water consumption per unit. The property management company uses this data to prepare utility cost statements.

Räbmatt residents can access current production and consumption data and the daily building load profile at home via their computers, tablets or smart phones (see photos). Visualisation will be enhanced this year to display own consumption for the past days, weeks and months, as well as the heat and water consumption of individual customers. This will help them optimise energy consumption.

Important experience

Räbmatt is a kind of pilot project for EWS. "The photovoltaic systems and solutions with private consumption communities are a trend for new construction projects. If the system design is not too large-scale, it is possible to save costs," says Gwerder. For EWS is it important to acquire experience in this area in order to play a leading role in this growth market.

EWS can use project learning as well as experience with the digital smart meter and with the energy data management system in other ways, for example for the meter roll-out for its approx. 25,000 customers, explains Gwerder. The Energy Act that went into force on 1 January 2018 requires mechanical meters in households to be replaced with smart meters. By the end of 2027, producers and end users in a given grid region will have to replace 80 per cent of mechanical meters with smart meters. The remaining 20 per cent can stay in service until the end of their functional life cycle. EWS has already installed some 2,000 new smart meters in its supply region - smart meters like those being used in Küssnacht.

The Räbmatt project is a true win-win solution, not only for EWS. The use of the most modern construction methods and technology, as well as locally produced, renewable energies is sustainable and good for the environment, helps minimise costs and promotes efficient energy consumption.