Green Smart House Solution - Max-i Fieldbus

For many years, lighting in buildings has been implemented with simple point-to-point connections between wall switches and lamp outlets in the ceiling. This is easy to overlook and install by any electriciant, but it is very difficult to rebuild - especially in low energy houses with an unbroken vapor barrier between outer walls where it may be necessary to remove the ceiling. It is also very difficult and expensive to make green sustainable solutions and add even the simplest smart-house features like dimming.

• You can replace the wall switches with mains dimmers, which reduces the average mains voltage, but there are a lot of disadvantages with this method:
• Most dimmers can only control one lamp and therefore cannot replace a double switch.
• There is no or very limited ways to implement more advanced features like multi-way (landing) switching, all-off and remote control.
• Because most LED-drivers and LED-bulbs have a capacitive input, the dimmer needs to be a trailing-edge type, which is much more expencive than a simple leading-edge TRIAC dimmer.
• There may be a minimum wattage, with can be difficult to fulfill with LED lamps and may require a resistor, which burns off energy all the time.
• The flicker-free dimming range is usually very limited - often to only 10 %, which the eye only regards as a 2.7 times reduction in light intensity.
• Induced currents may get the LED lamps to glow all the time.
• You can replace the LED-bulb with someone with wireless control such as WiFi, Thread, Bluetooth, Zigbee or Z-Wave, but this too has many disadvantages:
• Even more electronics is needed in each bulb and with that even more ressources to manufacture, reuse and/or dispose the device.
• The bulbs need to be powered up permanetly and must therefore not be forgotten in off-state.
• It may be necessary with routers, border routers, gateways and the use of advanced control devices like smartphones.
• Wireless communication may be disturbed by other communication in the same band and may be jammed so that for example alarm systems either don't work or create false alarms.
  
• Wireless communication may be hacked without physical access to the system and may even open a back door into your computer network on the wrong side of the firewall so a very high degree of safety and credibility is needed. The manufacturer must be trusted and must guarantee that all devices are safety updated even several years after the purchase! In practice, this may be impossible - especially with low cost devices.
• Safe wireless systems like Matter over Thread require a fairly expensive microprocessor with an advanced (128 bit) cryptographic engine and a lot of software layers on top of each other like TCP or UDP, IPv6 (128 bit) addressing, block-chain technology etc. Below the surface most such systems are insanely complicated, which makes it extremely difficult to handle by yourself if you don't have a finished protocol stack, and it may cause a lot of headacke if something don't just works out of the box. If a smart house system cannot easily be serviced, safety updated, rebuild and expanded for a very long period af time and not just by the ones, who have installed it, it may reduce the selling price of the house!
• All devices must usually be certified and go through a time-consuming and expensive conformance test.
• Systems like Matter, which standardize the interoperation on device level, will never be able to cover new, advanced features.
  
• It can be very difficult or even impossible to ensure that such systems do not send information about your behaviour to Google and others.
• You can replace the mains voltage LED-bulbs and with that perhaps also the entire lamp with someone, which is driven by a separate LED driver with remote control such as 0-10V, 1-10V, DALI, KNX or DMX512. This makes it necessary to rebuild the lamp outlets, ensure proper cooling for the LED drivers, which can be very difficult if they must be mounted in insulation material, draw new cables for the control system and add and use more advanced control devices than simple wall switches.
  

Very often, traditional smart house systems are driven by small batteries or mains voltage, but there are a lot of disadvantages of both methods.

• Battery powered devices are often chosen because they are easy and cheap to install, but the batteries have a lot of disadvantages:
  
• They require many resources to make and recycly. For example, it requires approximately 270 Wh to produce a single AA alkaline battery, but the stored energy is only approximately 3.9 Wh, which is 70 times less, so battery-driven devices are very far from being green if they are not rechargeable.
• Battery leakage can cause bad connections and corrosion.
• Small batteries do not have power enough for example for intelligent and fail safe alarm sensors and for solenoid driven devices like locking pawls.
• They must be replaced fairly frequently if a device is to be expected to work. This can be difficult for elderly people and it is a very big problem for actuators like radiator thermostats, locking systems and access control because the battery voltage may be high enough for stand-by, but not for operation, so a bad battery or a corroded battery connection may not be detected before it is too late.
• Mains driven devices including LED bulbs and chargers include an AC-DC converter, which has a lot of disadvantages too:
• It increases the price and size of the device considerably and may even be a clumsy "brick" on the charging cable as it is usually the case with laptop's and tablets.
• It generates electrical noise.
• It may turn off for a short time in case of transients or voltage drops.
• It may cause a risk of fire and/or shock due to the high mains voltage level and often very doubtful quality and cooling.
• It require big resources to make and are difficult to recycle due the the use of toxic epoxy boards and big components with the result that the device often just end up as waste in the incinerator or even on the landfill.
  
• It limits the service life of the device considerably - typical to less than half, which makes the waste problem even bigger.
• The necessary conversion to and from mains voltage makes it very expensive to utilize a house hold battery and solar panels to save energy, as an inverter is needed to generate AC. This also significantly reduces the service life and reduces the efficiency at low power level.
• It often results in a chaos of socket outlets, chargers and cable spaghetti on the floor with very low "Woman Acceptance Factor" - WAF.
  

 

The 100 W of both USB-PD 3.0 and Quick Charge is due to the safety standard IEC 60950-1, which specifies a maximum power of 100 W and a maximum current of 8 A. In this way, "the maximum apparent power and fault current available on the outlet under any load conditions including a short-circuit are limited to magnitudes not likely to cause ignition under fault conditions in connected equipment mounted on, and constructed from, suitably rated materials." Higher power and current levels should be used with great care - especially if a USB-C connector is used as a standard USB-C connector and cable can only handle 5 A continuously!

Since the charging voltage of a 20-V battery fits very well with the maximum-power-voltage of 54-cell solar panels depending on the voltage variations of the battery, such panels may be connected directly by means of a simple Max-i controlled switch as shown on the drawing. This saves the traditional charging controller. The charging voltage is simply set by connecting an appropriate number of solar panels, which changes the charging current in steps of typical 20 - 180 W depending on the sun light. Even in case of a failure on the battery connection, the load dump transient, which occurs until the panes are disconnected, is limited to approximately 35 V (open circuit voltage of the panels), so there is never any shock hazard, which is especially important in case of fire extinguishing by means og water, which may be very dangerous on traditional high-voltage systems.

In sunny areas, it may be possible to drive the devices totally off-grid even in the winter, and the excess power in the summer may then for example be used to drive a ventilation heat pump and additional 24-V heating elements so that the house gets ventilated and additional heating is not needed most of the year, which can save a lot of energy. The outlet of cold, dry air from the heat pump can even be used for a (supplementary) compressor-less refrigerator to squeeze the last efficiency out of the system and make the household even less vulnerable in crisis situations. As the global temperature is rising (AGW) this is especially important in areas, which are often hit by hurricanes, but the war in Ukraine has also shown that the first thing an enemy will do is to destroy the power infrastructure. Without electricity, the citizens has no light, no communication, no heating, no water and after just one week, any food in freezers and refrigerators may be destroyed so they may even starve. The ability to run off-grid (islanding) with the most important parts will therefore become more and more important in the future and with Max-i, it is possible to realize this at a very affordable price and without any shock hazard in case of floods or damages, which must be repaired. Even though many traditional photovoltaic systems have batteries, they generate AC for the grid and must therefore have "Grid - Anti-islanding" to prevent that a disconnected grid is powered up and therefore becomes dangerous to the utility workers, so the majority of these cannot run off-grid, and the few ones, which can, are very expensive.

Max-i is also the ideal replacement for the traditional 12-V systems in mountain huts without any grid connection as the higher voltage is better suited for LED lighting and can be used to charge and drive laptop PC's directly. Besides, the multi-drop line is easier to install in a nice way than point-to-point connections between buttons and lamps.

If there is not enough solar power to supply the system in the winter, a grid-powered charger may be necessary as a supplement, but it can be quite small and thus inexpensive as it should only be able to deliver the average power. Besides, it can charge the battery when the grid is low-loaded and/or the share of renewable energy is high and thus both save money and CO2 emissions. Of cause it is also possible to add a 230 Vac or 115 Vac inverter directly to the battery and in this way sell excess electricity to the power grid and/or install high voltage outlets, which may be used to drive equipment, which cannot be driven from 20 Vdc. The inverter must however be switched off in periods where it is not needed (loaded) as it would otherwise drain the battery.