The secret to living off the grid

Can one live entirely off the Grid?

Like it or not we have a world-wide shortage of power. In India and South Africa regular power outages have become the norm. Inverter and generator sales are going through the roof.  However, getting off the grid is not always that simple.

6700 T3 genset

Whilst generators burn fuel and make a noise they are or can be your best friend. If your household is running entirely off LPG for cooking and washing then all you need will be power to the lights and TV plus a couple of other low current draw items. A kettle is not one of these. A 1kW generator can supply a house lighting but not necessarily the TV and audio. 4kW generators have become very popular for this purpose and are available at a good price. Inverters are clean, can be coupled to a solar array to charge the batteries but in terms of cost, from the cheapest 5kW system to the most expensive, 2 to 5 times more expensive than a 4kW genset. These prices are related to sole inverter / batteries and the more expensive inverter / batteries and solar system. Some engineers peg current solar systems at about 2 dollars per watt (currently but dropping). A 5kW diesel generator costs about $1700.00 or 34c per Watt. Prices of gensets are more or less stable but the reality is, genset pricing does fluctuate according to demand and at present the more budget variety are shipped in from China. For a 5kW system powered by inverters, batteries and solar a buyer would be looking at approximately 10 000U$, not exactly chicken feed. However, a budget 5kW system could be had for about 4 000U$ without installation. The imported inverter may not last as long as that from a well established company but at present we would not know – inverter prices have dropped substantially as newer technology is incorporated. And they are very reliable.

Genset irritations – frequency

Users of gen-sets, myself including, have found some minor irritations when using a genset.  UPS not locking, microwave ovens not working and over-heating of an APC line regulator. The problem in every case has been genset frequency – designed for 50 or 60Hz but running half load at a much lower frequency.  This poses a problem when using appliances which utilise a mains transformer designed for 50 or 60Hz. The core, usually EI laminations of steel, is designed for this frequency and as the frequency drops so does the efficiency. Losses are incurred, released in the form of heat. One can get away with a 50Hz transformer running at 60Hz, but not always at 40Hz. And yes, gensets do sometimes drop to 40Hz. Generator inverters are more stable in this regard but cost a whack more. Large generators, gas or diesel, have very sophisticated mechanical and electrical governor controls. With a hefty price tag. You do not have this on portable and lower priced gensets.

Microwave ovens all have magnetrons, a self oscillating thermionic tube. The magnetron heater voltage, if designed for 6V, may not oscillate at lower heater voltages but usually at the very least, radiation energy drops substantially. On lower genset frequencies the platter or turntable motor also slows down. So make sure your generator output capacity has been rated properly. In our troubled times any mains frequency locked timers are just not reliable under standard generator power. (frequency fluctuations). A big irritation of course is that they are so much more reliable than the so called high current over the counter digital timers.

Inverter woes – output waveform

Inverters are not without their problems either. Most affordable inverters are rock steady at the given output frequency but the output is a modified sine wave.  In simple terms, the output is a square wave derived from direct current and wave-shaped by inductors and capacitors or reactive components. This square wave can be run at many kHz or at 50/60Hz. Without embarking on a tedious technical explanation, inverters have improved in leaps and bounds over the last 5 years, especially with the use of IGBT (Insulated gate Bipolar Transistor) which allows huge switching currents at very fast switching speeds. When driving a switched mode power supply which just so happens to use similar circuitry they can be mated almost perfectly. However, driving a mains laminated core transformer from a UPS or modified sine inverter sometimes is always not that easy – a UPS is designed to power a computer as a back up supply.

Living off the grid - Voltronic Inverter
Voltronic 1kVA Pure Sine Wave

SMPSU aren’t usually fussy about the frequency being too high or too low, neither the voltage sagging – they will control, switch and regulate. Mains transformers may not like the harmonic content output of the inverter (or UPS) and in some poor designs the low frequency transformers run hot (square wave content / harmonic energy dissipation) or switching can be heard through the loudspeakers of an amplifier.  The general rule of thumb is not to connect your class A or AB amplifier to a UPS. If the amplifier is powered by a switching power supply this should then be OK.

Using a UPS on an inverter to prevent drop-out

A problem that does arise through inverter use though is when a user connects a UPS to the inverter to prevent drop-out when applying the mains load transfer switch. Some inverters, usually the line interactive variety, switch to battery power. Manufacturers claim that the inverter output is dirty. Some say the frequency is off.  Whatever. A UPS is micro-controlled and looks at many variables,  voltage and frequency being two of the criteria. Contamination of either (voltage distortion and frequency lockout) will cause the UPS to switch to battery. In my experience some UPS do not see a pure sine wave input, glitches or any unusual line activity which will cause the UPS to transfer to batteries.  Where we do pick up problems is that the power supplies, and these are predominantly switched mode units of television receivers do not always like the inverter or UPS output waveform and in one particular case, a plasma screen power supply blew twice before the owner realised it was in fact the UPS causing the failure. (An APC UPS cured the problem – the problem was the plasma movistor, or anti-surge component in the power supply). Sounds ambiguous but remember this is not for all cases – many TV receivers run happily on a UPS, in fact most do. If you are fortunate enough to have a friend with electronic test equipment it’s a great experiment to check your UPS or inverter output wave shape. Don’t do this if you have no experience in using an oscilloscope though – one may need to use isolated or differential probes to make the tests. Carry the tests out to pure resistive and reactive loads to get a good idea as to how bad it can get.

SCR switched inverters

Years back most inverters used SCRs for switching. Although they could muster up enough courage to drive huge inverter switching transformers many engineers shied away from this technology – bear in mind that the currents were huge, cables were 200A welder gauge and they were cumbersome to work with, using point to point connections.  Modern fast switching devices are all PCB mount with the only heavy cabling taking place between batteries and IGBTs. One 600W pure sine wave inverter I was tasked to repair had 30 2N3055s (15 per leg) in the output switching stage. The unit weighed over 200kg. (with batteries). Modern 1000VA UPS and inverters can weigh as little as 5kg depending on battery size. It must be stated that modern technology has made these devices very reliable – indeed the only thing eventually failing over a 5 year period would be the battery.  Most electronic failure is due to user ignorance. A typical problem waiting to happen is connecting anti-surge devices after the UPS.

Although engineers will often argue the merits of line interactive UPS over double conversion units, the trend is that double conversion can eliminate many of the weaknesses associated with the use of gensets but not necessarily that of inverters. Inverter power is essentially the same as that of online UPS (double conversion) AND line interactive – both UPS types work equally well if only used when there is a power outage. Since we are living off the grid who really cares – charge the batteries through solar, wind or generator, switch the UPS or inverter on when you need it.  Online UPS are favoured for genset use. They also often have a higher continuous current rating. If you do have an online UPS of considerable power, rather use the UPS as the sole source of power, possibly with extended run time batteries and not connect them to an inverter. This gets switched on when you need the power otherwise both online and line interactive draw power from the battery, no matter how small. Use batteries to power LED lighting. Use the online UPS to power the TV receiver.  This may all sound confusing but what is the end result you are looking at? Light and heat. Heat means huge current drain. Generating heat in most cases is heavy on LPG as well. Always have a backup supply handy – you may not have light and you may not have wind. To my mind the solution is always around the use of LPG, a small reliable DC generator and of course, solar panels.

Going off the grid means you will have to get a generator, no matter how small, for real emergencies. This would be to power critical lighting and charge batteries. Solar arrays are great if you have the finances but there will be a time when nature takes it’s own direction and there may be inadequate power to charge the batteries for critical circuits. Interestingly enough, if one had to look at real emergencies and people whom have come back from life threatening ordeals unscathed, the best fraternity to gain insight from would be your deep sea fishermen or yachtsmen. They live off the grid – DC power is king. There are many forums associated with living off utility power, a wealth of real-world experience and of course, serious solution providers. A yacht out in the ocean is a house on an island.

Interesting topics and head scratchers:

  • NIFE cells
  • Rotary converters
  • Briggs and Stratton / automobile alternators
  • Early submarines and DC power

And again, my Kipor 6700T refuses to start this morning.

Genset driven UPS (Uninterruptible Power Supplies)

UPS and Generators (marriage made in hell)

The harsh reality of many gensets used in the home is that they will enable switching between mains and battery of a line interactive uninterruptible power supply.  This will inevitably cause eventual shut down of the UPS when the battery becomes exhausted or low voltage is sensed. If your backup supply is beeping at regular intervals ensure that it’s not going onto battery mode to drive the inverter. (if in doubt read the manual).

An online supply is one in which the AC is converted into a high power DC supply, which in turn drives an inverter for alternating current out. Although much more expensive than a line interactive supply they do not succumb to switching between mains and battery when it detects low or high voltage and frequency fluctuations. Diesel generators, even smaller units, are better at driving a line-interactive UPS than petrol generators because of their higher torque at lower rpm.

UPS - rockmountables[ ATTRIBUTE: Jimmy Thomas “Dark Server Room” ]

The Kipor 6700TA or in that particular series is a popular genset used in the home and can drive most line interactive supplies without picking up problems even when the frequency runs as low as 40Hz (tested with a Vanguard 2000 rack mount). The VGD series is online and worked 100%. All the line interactive supplies tested on this generator worked 100% also, even with a 2kW load on the genset. (APC, BNT, etc). Running a 4.5kVA petrol genset caused the backup supplies all to beep when the load was set to 2kW but ran comfortably once the generator speed had stabilised (45-55Hz).

Some inverters allow for generator input, the inverter can be used then as a stabiliser, depending on what type and how it’s wired. These inverters are fed from batteries as well. With a solar array acting as a charger, batteries and a generator most home owners can run entirely off the grid even with a 5kVA system as long as there is no overload – use gas geysers and cookers. Kettles and toasters draw a fair whack so they should in theory be eliminated if possible. Who needs a toaster when there is a power outage in any event?

Electrical supplies, especially those used for backup power can be very sophisticated. 99% of this is due to the use of 50 or 60Hz a.c. and the 110 or 220V line voltages. Your supply utility frequency is usually rock steady, the voltages not so.  With small generators we have a problem with both voltage and frequency stability. The line interactive supply does not like this. The online variety can handle it.

UPS have another inherent drawback – their output wave shape. This applies to ‘modified’ sine-wave inverters as well.  Besides for the very expensive pure sine wave device most are modified square-wave (to get sine of course).  If an inverter drives a line interactive supply we may end up with the same problem as the genset line interactive supply issue. Dirty waveforms are not welcomed by the line interactive device. Again the backup supply may go into battery inverter mode.

The truth of the matter is that the best uninterruptible supply for this project is an online supply to feed switched mode power supplies and non-inductive loads (not transformers and a.c. motors). Modifying a line interactive supply by ensuring there is adequate ventilation and fan-cooling one can build a charger/DC regulator to drive the inverter stage very much like the double conversion process used in the online UPS.


 

 

Fall in line with Geek Speak and BBB

Geek Speak and the Triple B

In a previous article we covered the internet of things which to sum it up really means interconnectivity. Possibly using the TCP/IP protocol. Financial news correspondents love using phrases which are meaningless, maybe your broker as well. Fancy terms are either lost on the audience or just really means zilch to them. Use real words and a real language.  Of course if you have a product and you need to sell it you don’t tell people why they should have it but rather what would happen if they did not have it. Fear is the biggest driving force – the biggest seller – from newspapers, to artillery and sports cars. Imagine not having to fear that your neighbour has a better car than you, that you don’t need cable TV or a motor vehicle with pedals in case you run out of gas.

Most autobiographies will give you a glimpse at the mistakes the author made before or after they became famous. Bill Gates is one. “The Road Ahead”. He does not suffer from ‘swelling of the head’ syndrome. Neither does he use techno-babble speak. Likewise Richard Branson’s “Losing my Virginity”. Both great reads by the way. So why didn’t they use geek speak when writing their books whilst quite obviously they are both technologically driven individuals?

bbb

I is a Manager

Many years back I had the displeasure of sitting with a chap whom used to service medical equipment for a living. Using fancy terms for all the equipment he worked on, fancy terms for the money he made and fancy terms for his success. He forgot to tell us that he had just recently been retrenched though. He was a walking talking inferiority complex.  Now if he had devised a machine which cured diabetes would have been another story entirely.  One of the best technicians I have met seldom spoke. He’d go in, do the job and move on to the next. The worst technician used to give a great rundown of what he was about to do, how he was going to do it and of course with much fanfare and fireworks did half a job. We all know someone  like that so this is not something new. They make the world go round.

Summing it up with Thevenin

So why an article on Geek speak?  In the world of computers I found the most fascinating teachers were the ones that explained in plain English (or any other language of your choosing).  My own analysis, rightly or wrongly is because they understood the concept so did not have to cloak the explanation in symbols and hieroglyphics. Many years back, as a dumb-arsed first year student I asked our lecturer in the electronics class all about Thevenin’s theorem. Of course I had just read up on it so this was a simple test – student vs college prof. I failed dismally – taking an approach which was so simple he made all my understandings of Thevenin’s thereom look mediocre. And of course he made us write a test the following day on this same subject which I then did pass, based on his explanation, not my theories. Here was a guy whom could put an entire book into one easy 60 minute lecture. This sort of sums it up – bullshit baffles brains. Or rather: “Merda taurorum animas conturbit”.

Merda taurorum animas conturbit Vs Geek Speak

The Internet of Things is merda taurorum animas conturbit. Like car torques, horsepower and fuel economy, GPU speed and PMPO. When your avid listener’s eyes glaze over you know you have made an impact. Like the salesman whistling through his teeth when he tells you that “that capacitor is expensive”. What he is telling you is, “man, you must just check my mark-up”. Although geek speak is associated with the computer gurus, BBB is associated with politics and economists.

Detection circuits

  • Name dropping
  • Forefinger wagging
  • Using large non-descriptive words
  • Output is usually in the form of ones and zeros or Hex and is spoken at a Baud rate

And to close off this round of BBB

When Albert Einstein died, he met three New Zealanders in the queue outside the Pearly Gates. To pass the time, he asked what were their IQs. The first replied 190. “Wonderful,” exclaimed Einstein. “We can discuss the contribution made by Ernest Rutherford to atomic physics and my theory of general relativity”. The second answered 150. “Good,” said Einstein. “I look forward to discussing the role of New Zealand’s nuclear-free legislation in the quest for world peace”. The third New Zealander mumbled 50. Einstein paused, and then asked, “So what is your forecast for the budget deficit next year?”