Bidirectional “Vehicle to Home” for VW ID. models complements home photovoltaics
Volkswagen wants to “help reduce energy costs and at the same time contribute to the sustainable use of energy” with a bidirectional charging function for certain VW ID. models. Unfortunately, the offer sounds better than it actually is.
Anyone who owns a house with a photovoltaic system knows the problem: most of the electricity flows when you only need a little of it. At night, however, no electricity is generated at all. However, because the system is almost always dimensioned so that meaningful amounts of electricity can still be generated, at least during the transition period, the majority of the surplus production can only be fed into the grid for modest compensation.
A power storage system changes everything. It makes it possible to store the surplus yield and thus sensibly reduce the area used to generate electricity, because the electricity can be used whenever it is needed. The biggest disadvantage of such a memory, however, is its price. Including provisions for replacement, it can take a long time for this investment to pay off – if at all.
Image 1 of 3 The wallbox is the physical link between the house and car batteries.
Owners of more powerful photovoltaic systems often do not live in the (inner) city and therefore often use a car to get to the next train station or to work anyway. In this case, the connection between photovoltaics and electric cars is obvious and is therefore used frequently. If you can take advantage of the car’s bidirectional charging option, in most cases you can avoid the need for expensive electricity storage. The car already offers the option of an electrical clipboard and thus the possibility of supplying a house with solar power even over several cloudy days.
According to ISO standard 15118-2
Unfortunately, the range of such vehicles has so far been very limited. The mass manufacturer Volkswagen is now partially changing this and is upgrading its electric cars to include the useful “Vehicle to Home” function. Volkswagen will initially equip its ID. models with the 77 kWh battery with bidirectional charging function. This also applies to vehicles that have already been delivered after their owners have updated the operating system with ID software 3.5. This gives the vehicles the opportunity to communicate between the electric vehicle and the wallbox in accordance with ISO standard 15118-2. This is the basis for bidirectional charging on the DC charging standard “Combined Charging System” (CCS), which is the most widespread in Europe.
Unfortunately not entirely consistent
Volkswagen sets the average consumption of a house at 15 kWh per day. This means that a full 77 kWh battery could ensure the power supply for around two full days, as the electronics do not allow the traction battery to be discharged below 20 percent SoC. Not so much to save the battery, but rather to keep the car drivable. To describe this calculation as “extremely conservative” is almost euphemistic, because 20 percent would correspond to around 15 kWh remaining in the battery. The assumed consumption of 15 kWh per day would therefore mean that 80 percent of the battery is enough for four days.
However, the Lower Saxony manufacturer’s offer is not completely consistent. There must also be an electricity storage system for the house. Volkswagen writes: “The function (…) in combination with the DC charging technology is an extension of the home storage. This takes over the main energy supply of the house. The vehicle is activated by the home power plant when the home storage needs additional energy. As soon as the home storage is back Once charged, the vehicle stops transmitting energy and goes into standby mode.”
Another catch in Volkswagen’s offer: The first version works exclusively with the DC home power plant from the “S10 E COMPACT” series from HagerEnergy GmbH, which has a capacity of almost 9 kWh and costs 12,500 euros. The possibility of connecting to domestic power plants of other origins will only be activated later. Given the conditions, the offer seems more like a technological gimmick for enthusiasts than an affordable and profitable component for the energy transition.
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