Wednesday, May 10, 2017

Time that Home Appliances are made available in DC, too.

This Post is somewhat  a  sequel to  my earlier one in Novemeber 2016.

I made certain improvements for better data collection and utilization of electricity generated from my 2 KW roof top PV panels.

1) Extended the connection to Ground Floor with a change over switch and requested the tenents to use solar energy from morning  8 am to 5 pm everyday.  This had improved the average generation from 6.5 kwh per day 8.5 kwh  due to live consumption.

2) I attached a separate energy meter and measured the actual consumption. I wanted to know whether what is being generated is fully utilized or lost something due to inefficiency.

This is where I had a shock to find that only just about 55 %-60% of the generation is accounted in useful work. A closer watch helped me to understand that 25 to 30 % is lost in the MPPT inverter which goes on converting DC to AC  or AC to DC back and forth.

My search through internet revealed that each time  when this conversion takes place, there is a loss of 12 %. To put it simply  1) Solar to Inverter ( DC to AC)- 12% 2) Inverter to Battery ( AC to DC) -12% and  again Battery to Inverter ( DC to AC) another 12% ie  about 36% . This may vary with type of electical load, time of utilization, temperature etc.

Just see the values I recorded recently below :

What is shown in the red color is the consumption by the inverter for every kwh (or units) it deliverd. This is pretty constant showing that we are losing  0.41 kwh for every kwh used.  That is HUGE !!

What I understand is that, it is inevitable if we continue to use  230V AC home appliances. Best way  to reduce this loss is, to use appliances that run on Direct Current (DC).

Incidentally the DC appliance needs lesser energy compared to AC appliance to do the same job. For example  a 60 watt, AC ceiling  fan  can be replaced by  27 watts DC ceiling fan. This is attributed to better torque delivery by DC machines.
An interesting study at NIIT Trichy,  published in Dec 2016, showed that to operate a home wet grinder of same capacity, the DC motor needed lesser energy as compared to conventional AC motor.  This in turn reduced the number of Solar panels from 12 to 6 !!   They found similar trend with a dough making machine also.  IIT ( Madras) too taking efforts to promote the concept of Direct Current utiliztion in micro grids  to reduce the conversion losses.   

For a wider acceptance of solar roof top electricity generation, thus, the home appliances need to be made available by the OEMs ( Original Equipment Manufacturers). This also reduces the size of solar panels and overall investment to a great extent. This should dawn on the Policy Makers.

Now, Government  should step in - like they did to promote LED bulbs- through some subsidies or tax incentives to develop and promote DC appliances including refrigerators and air conditioners. This will pave way to decentralize energy generation towards self sustaining economic model.
I am sure in a few years this will become a reality and hence  I can do More with my investment than what I originally thought !!