Grid-Tie Inverter

In land scarce Singapore, it is very difficult to go completely off grid. Off grid means that you no longer need to depend on SP services main power to supply your household's demands on electricity.

Off-grid system requires backup batteries to power the electrical appliances during night time and cloudy days. Batteries are heavy investment in an off grid system. They can easily take up one third of the cost of a solar generator system.

Batteries require regular maintenance and have limited shelve life, typically 2 to 5 years depending on the types of battery.





What is a Grid-tie Inverter? 

A grid-tie inverter is a device which convert DC power input, such as the power from the solar panels, to 230V AC power output which is commonly available in all household in Singapore.

It also synchronizes the sine wave of the it's output to match the sine wave of the AC main in your house.

 What to look out for in a Grid-tie Inverter?

1st thing you must check is what is the total output of your solar panels and the voltage of your solar panels output. For me, I have 6 x 30W panels and 1 x 100W panel with a total output of 280W at 12V DC. So I selected a 300W grid-tie inverter which is sufficient to handle the output from my solar panels.

The next thing is to check the output of the inverter. It should give 230V AC that we use in Singapore and not the 120V AC common used in North America.

Some people will also look at the efficiency of the inverter. For me, it just a small setup, so I look at the cost of the inverter, which is less than S$200.





How to Connect Grid-tie Inverter?

The setup is very simple, even more simple than the basic setup of using charge controller and batteries.

You just have to connect the output of your solar panels to the input of the grid tie inverter. Red for positive and black for negative.

Next you connect the output of the grid tie inverter, which is a 3 pin socket with the AC cable provided (similar to a PC power cable). Then you connect the other end of the AC cable to a wall socket.

You can purchase a AC power monitor meter like the one in the picture and place it in between the wall socket and the output of the grid tie inverter to measure the power produced by the grid tie inverter and hence your solar panels.





Which setup would I choose? Grid-tie or Off-grid


If you have solar panels of more than 100W, I would recommend that you go for grid-tie system. It is simple, with fewer components and requires almost zero maintenance. For smaller system of less than 100W output, off-grid system with small battery and charge controller is more cost effective and can provide you with more learning experience.

PM me (Cheehui68) in hardwarezone.com.sg if you need further discussion and help.

Solar Car Battery Charger

I own a small 1.1L car, Kia Picanto. I replaced my previous battery 6 months ago when it was about 2 year old and occasionally having difficulty in cranking up the engine. My car was then slightly more than 2 years to go before my COE expires in Feb 2016. I hope the new battery can last me more than 2 years so I do not have to get another one before Feb 2016.

Therefore topping up the battery charges to it's optimum and fullest potential becomes very important for me. I bought a 4.5W solar car battery charger (picture on the right) from DealExtreme to try out and regretted about it because it was under power and would take weeks to top up my battery to its fullest.

It comes with a cigarette lighter adapter with an LED indicator when there is enough sunlight to charge the battery. But I discovered that the circuitry to power the LED pulls down the voltage so much that it left with not enough voltage (below 12V) to charge the battery.

I ended up connecting it directly to the battery terminals and later on added a PWM charge controller because I was worrying of over voltage as I measured 19+V open circuit from the solar panel.




As I mentioned, 4.5W is too small that it will take weeks to top up my battery. The battery status of my 10A PWM solar charge controller always shows red in the morning before I crank up my car engine. I ended up purchasing a few 10W semi-flexible poly-crystalline solar panels from eBay and here's a short video of the 10W panel with 10A PWM charge controller.

With this Solar car battery charger, I now have the peace of mind that my car battery will always be top up to its fullest potential and will prevent lead sulfate from building up on the battery plates which will shorten the life span of the battery.

I have also added 2 10W panels to bring the total wattage to 30W so that it can top up the battery everyday.

Automatic Lighting

I have installed 2 sets of automatic LED lighting. One in my balcony and another in my common toilet..

They are programmed (using the charge controller) to turn on when it is dark - around 7.30pm and turn off after 3 hours - around 10.30pm.

Each set consists of a 30W mono-crystalline panel, a 10A solar charge controller, a 2nd hand car battery and a 1 meter LED strip.

The one at the balcony is also powering the solar fan occasionally. The LED lights in the balcony will shine into my living room, so eliminating the need to switch on my living room lights while we are watching the TV.

The one at the common toilet also lights up most part of the kitchen so we don't have to switch on the lights when we go into the kitchen to wash our cups, clothing, etc.

My wife and I are quite happy with the LED lighting as it brings us lots of conveniences.
I managed to keep the cost down (less than $100 per set) by using 2nd hand car battery from scrap yard.

Actually, I can simply use 1 set of this system to light up 2 places, but the wire will be very long and unsightly.

My Solar Energy Harvesting Begins to Bear Fruits

After a few months of Solar harvesting, my electricity usage has began to come down for the past 3 months. I recon that I am able to save about 100 kWh of electricity per month (Refer to my own record of actual electricity usage).
Based on current tariff of S$0.28 or 28 cents (inclusive of 7% GST), I estimate that I would be able to save S$28 per month which means I am able to recover my cost within 4 years.

But part of the reason for the electricity usage to come down could be because of the cold weather we experienced in Singapore these 2 months. The cold weather has resulted in lower usage of air conditioning. I would have to monitor the usage during hotter months, but for now I am quite happy with the result.

The higher gas and water usage shows that I am not on holiday during this period. I still wonder why my gas usage shoots up so high ??

Month	Amount	Est (*)	Own record	Electricity (kWh)	Gas (kWh)	Water (Cu M)
Jul-13	$152.85	*		372	49	13.3
Aug-13	$202.92			515	65	17.3
Sep-13	$180.03	*	413	451	58	15.6
Oct-13	$145.71		399	347	50	13.5
Nov-13	$151.29	*	349	367	50	13.4
Dec-13	$141.01		306	280	80	17.1

Update:
My electricity consumption has dropped to 73kWh in Feb, believe it or not?
Of course not. The actual reading is 170kWh, they had over estimated in Jan and made adjustment in Feb. I think it will stabilized to around 200kWh. That's a saving of 200kWh per month or $56 per month or $672 per year, which is 100% more saving than I expected.   

Activating Plan B

There is a saying - "we ought to prepare for rainy days". This is especially fitting when it comes to solar energy harvesting in Singapore. Not only rainy days but cloudy days as well.

Singapore is a tropical island country surrounded by sea located near the Equator. Most of the days are sunny, hot and humid except at the end of the year in November and December which is so called the monsoon period when heavy rains and thunder storms are common in the afternoon.

I have 3 x 30W Mono crystalline panels, 1 x 42Ah and 3 x 9Ah SLA batteries connected in parallel for a total of 69Ah capacity. I am running a 3W LED lamp for few hours at night, a 15W Solar fan running 8 to 10 hours overnight, a 6W LED strip running occasionally and a 2W handphone charger.
With my batteries, I should have 828Wh (69Ah x 12V) if fully charged, so they should be able to power my loads continuously for about 32 hours or 4 nights without charging if I run them 8 hours per night.



Under normal weather condition, that is mostly sunny with occasional one to two days of rain and cloud in between, my setup should be adequate. However, the reverse happens during this 2 weeks whereby most of the days are raining and cloudy with 1 to 2 sunny days in between.
Eventually after almost 2 weeks of working, my system sounded the first low voltage alarm at around 6.30am Saturday morning. I looked at the battery voltage and it was at 10.4V. I quickly switch off my fan to prevent the batteries from over discharge. The batteries were at 11.9V the night before.

Now I have 2 options. One is to expand my solar capacity to cater for rainy and cloudy days. Another is to use an AC battery charge to charge up the batteries.

If I opt for the first option, I think I would need to at least double my panel capacity from 90W to 180W, which means it would impact my ROI (Return on Investment) for at lease a few years. The other disadvantage of this option is that it would be over capacity during sunny period.


So I opted for the second option which is my plan B. Then I started to look at SLA battery chargers. The price ranges from S$18 to almost S$50. I am reluctant to spend extra money on charger and also have the fear that poor quality charger might damage the battery. I also read that we should not use charge meant for charging car battery to charge SLA battery, otherwise, it may cause gassing and explosion.

Then I remembered I still have an 10A PWM Solar charge controller laying around after I switched to the MPPT controller. This would be an ideal charger as it is designed to charge SLA batteries. I also have a Philips power adopter which I use to charge my Philips electric shaver.

The Philips power adopter output is at 17.2V which is well within the input range of the PWM charge controller. I then connected the output of the Philips power adopter to the panel input of the PWM charge controller and observed that the red panel LED lighted indicating that it is receive power from the "solar panel". I measured the voltage of the "panel" input and it read 11.89V. I measured the battery output and it read 11.86V. The charging green LED also blinking indicating that it is charging the battery.

The Philips power adopter is rated at 9W. I do not know how much charge it will put into the batteries. But so far it has been able to maintain the voltage above 12V with current weather condition of frequent rains. With that little extra electricity it consumes, I think it is worthwhile to go for the second option and implementing Plan B. I have decided that I would always use the AC charger to charge the battery if the voltage is below 12.6V.

With this plan B, it gives me the peace of mind that I will always have enough energy to power my loads in all weather condition and can sleep soundly without being wake up in the middle of the night by the low voltage alarm again.

Update: The Philips power adopter with it's 9W power is not enough to buffer me through a few consecutive days of cloudy sky and heavy weekends usage during the Christmas period. I ended up ordering a 2A battery charger from DealExtreme which should tide me through longer rainy days. The learning point is to get a charger that is sufficient to charge your battery than what you will consume for the whole day.

Review of my 15W Floor Standing Solar Fan

I bought a DC 12V Solar fan on 24 Nov 2013.
I have been using this fan for close to 2 weeks and I think it's time to write a short review of my Solar fan.

A little background on why I bought this Solar fan first. My solar power system consists of 3 x 30W panels hooked up in parallel. I have 3 x 9Ah and 1 x 42Ah 12V batteries connected in parallel also totaling 69Ah capacity. I have a 30A MPPT Solar charge controller connected between the solar panels and the batteries.

I used to power my Mitsubishi floor standing fan through a 300W DC to AC inverter. The AC fan together with the inverter consume about 55W of power.

I calculated that if my batteries were fully charged, I would have 828 Watt Hour (Wh) of energy for my usage (69Ah x 12V). With my intention of powering my floor standing Mitsubishi fan for 8 hours a night, I would need 440 Wh of stored energy (8hr x 55W). So my batteries are sufficient to power my Mitsubishi fan for almost 2 nights if they are fully charged.

The problem I encountered is that although my batteries capacity is sufficient, they do not get charge up fast enough. I observed that it took about 4 days to fully charge up the batteries with good sunlight. That works out to be around 200Wh per day. Though my panels are rated at 90W in total, I hardly get the full 90W energy. The most I observed is 65W from the display of my MPPT controller during peak sunlight and most of the time it is at around 15W to 30W.

This means that if I on my Mitsubishi fan for 1 night, I would have to wait for 2 days before I start to use it again in order not to deplete the batteries too much. So my next option would be to increase my solar charging capacity to at least twice the current capacity (90W), or to reduce my power consumption.

Increasing the charging capacity by twice would cost twice as much to get a 15W Solar fan. I am reluctant to get the 15W solar fan initially because I felt that it would not be as powerful as my current 55W Mitsubishi fan. But after thinking about the hard work of having to mount another
3 x 30W panels and the cost of them, I decided to give the solar fan a try.
The solar fan consumes merely 15W at high speed. This means my 828 Watt Hour batteries would be able to power it for around 55 hours or almost 7 nights if I use it for 8 hours per night. This would allow ample time for my batteries to get charged up without depleting too deeply.



How does it perform?
I got the fan from Tanericash on 24 Nov 2013, Sunday night around 8pm. A quick test at his place to make sure that the fan works and it sounds powerful enough.
I got back home around 9pm and quickly setup and connect it up for testing.
My wife was a bit surprise as from the appearance of the fan, she did not expect it to perform as powerful. But I quickly noticed that the wind at full speed was not as powerful as the wind of the Mitsubishi fan at speed 2. It is quite noisy and the noise gives the impression that it is powerful.

I had a feeling that the fan blades are too small and slim to produce strong winds. So I took the Mitsubishi fan blades and installed onto the solar fan. But the Mitsubishi fan blades are too heavy for the small DC motor that it not only turn more slowly but consumes more power (20W).

I continue my search for a suitable fan blades and then came across a Toyomi AC fan with 5 blades. I tested the fan at OG and found the wind to be quite powerful. I called up Toyomi agent and was quoted $18 for the fan blades alone. So I search in Gumtree and manage to get a used Toyomi fan at $15.

I replaced the original fan blades with the Toyomi fan blades. The performance of the fan improves and it runs much more quiet. The wind power is still lower than the Mitsubishi fan at speed 2. It is acceptable during this time of the year when the temperature is cooler.

So my conclusion is that if you are using you AC fan normally at speed 1 or 2, you may find this solar fan suits your needs. If you are a person who need fan speed at 2 or 3 to be comfortable, you may find this DC Solar fan is under power.

Update: I was a little bit disappointed with the power of the solar fan, so I actually tried to look for DC motor to replace the original solar fan motor.  I also searched the Internet to see whether there are more powerful solar fans available. While I was searching, I noticed that my solar fan input accept voltage ranging from 12V to 18V. It struck me that may be I could increase the voltage to increase the power. I have bought a power booster previously for charging my electric shaver which requires 17.2V input. So I connected the power booster output to the solar fan and to my delight, the fan speed increases and the wind becomes very strong, although it ended up using more power (around 30W). I then tune the output voltage of the power booster to 14.5V so that it uses less power and yet providing the powerful breeze I needed.

Now, it consumes about 23W on low speed and 26W on high speed. I am very satisfied with the solution although it consumes slightly more power than the original setting, it achieves the amount of air flow I require for sufficient comfort level.

Watt is that? How to size your solar power generator?

Watt is that?

Although it is not necessary to know the terms commonly use in a solar generator setup, a basic understanding of the terms can help you to estimate and size your solar energy system to meet your energy needs.

Watt is the unit used for the measurement of the amount of power. It is the product of Voltage and Current, that is when you multiply voltage (V) by current (I), you get Power in watt. (P=VI)

Voltage (V) is the potential difference between 2 points, say point A and point B. When point A is higher than point B, there is a potential difference which is measured by Volt. The bigger the difference, the higher the Voltage.

When there is potential difference between 2 points, electrical energy will flow from one point to another just like water flowing from a higher ground to a lower ground. The amount of electrical energy flowing through is known as Current and is measured in Ampere (I).

As for Resistance (R), I see it as a slope between point A and point B, the higher the Resistance, the gentler the slope and it will take more time for the same amount of electrical energy to pass through.


How to size solar power generator?

First, we need to know the appliances we want to power by the solar energy. The electrical appliances in our house are usually rated in Power or Watt. For example, an electric fan is rated about 50W. Second, we need to know how many hours we want to run the appliance. Let's say we want to run it for 8 hours per day. Then the energy we need to power the fan for 8 hours is 8 x 50W = 400Wh (Watt hour).

So your solar panels would need to generate at least this amount of energy. If you are staying in landed property, you can probably get 8 hours of sunlight. But you don't always get the full intensity of the sunlight due to cloudy sky and the angle of the sun beam, so you would have to discount that by say 1/3. If you are powering the fan through inverter, you have to factor in another 10% to 20% loss. So I would say it's better to over estimate and get a bigger capacity panel. In this case, I would suggest go for a 100W panel. It's very difficult to estimate the actual panel size you need as the amount of sunlight receive varies from places to places. For those of us staying in HDB flat, we may need to double the size of the panel as we are only getting the morning or afternoon sun.

After you have estimated the power of the panel required, you need to size up the battery required to store the solar energy if you are going to use the energy at night. We have calculated that you need 400Wh to power the fan for 8 hours. If you are going to use it only at night, you would need at least 400Wh / 12V = 33.3 Ah battery to store the energy generated by your solar panel. Battery is usually rated in Ah and I am assuming that we are setting up as 12V system. But it is better to get at least twice the capacity you need because it is no good for the battery to be always drawn down more than 75% most of the time. That will shorten the life span of the battery.

The last thing to size up is the charge controller. Charge controller is normally rated in Ampere (A).
A 50W solar panel will produce about 4.2A at peak power (50W / 12V). A 50W fan will also draws around 4.2A. If you want to power an LCD TV which draws about 100W, then you need a higher rating charge controller to handle the higher output of around 8.3A.

I hope this short write up will help you in sizing up your system. This is more of an art then science. You can always try and error to get the most ideal setup for your energy needs.

Also begin small and add on when needed.
If you find that your battery depleted within the same day (you get low voltage alarm and cut-off from the charge controller), then you need to increase your battery size. If you find that your battery depleted after a few days, then you need to add more panel. If you find that you battery is always full, then you are doing great, you can try to run more devices.

Cheers!

Review of my Taiwan made MPPT Charge controller

This is the third solar charge controller that I own.
My first charge controller is a China made 10A PWM (Pilse Width Modulation) charge controller.
It has a very simply display using LEDs to indicate the state of charging, for example green for good, red for low and blinking red for overload or over discharge.

I wanted a charge controller that provides better indication as the charging voltage, charging wattage, charging current and the output or load wattage. So I purchase a second charge controller. It was a 30A LCD PWM charge controller which provides the above mentioned perimeters.
However, this LCD PWM charge controller started to give wrong voltage reading after 1 or 2 days. I was using 12V batteries but the display on the LCD shown more than 18V and sometime even more than 20V during night time when there is no sunlight.




So, after reviewing some solar charge controllers on YouTube, I decided to purchase my third Solar charge controller from ebay.It is a 20A MPPT (Maximum Power Point Tracking) solar charge controller which is made in Taiwan.

It costs almost twice as much as the 30A PWM LCD charge controller but after using for more than one week, I think is worth the extra money.

I found it listed on ebay and corresponded with the seller on shipping cost. They responded to me on the same day and I was impressed with their prompt reply.

So I placed my order on 11 Nov which is a Monday. I was presently surprised that the controller reached me on the same Friday.
It was well packaged and the quality of the controller is much better that the China made LCD controller.

For PWM charge controller, the voltage at the panel input is always slightly higher than the battery voltage which is usually between 12V to 13V depending on the charge of the battery. Whereas for MPPT charge controller, it will monitor the incoming voltage and the battery voltage to determine the best voltage for charging the battery.

This morning, around 8.11am, I measured the incoming panel voltage to be around 17.8V. This is not possible for a PWM charge controller. When you see such a high voltage when using a PWM charge controller, you have to check the battery terminal voltage immediately. If the battery terminal voltage is also at above 17V, there is a possibility that your charge controller is faulty and you risk damaging your battery if you continue to allow the battery to be charged.




I then measured the battery voltage and it was at around 13.2V. This confirmed that the MPPT charge controller is working normally.

I am happy with this MPPT charge controller. The other good point about this charge controller is the useful information displayed all at once on the back-lighted LCD display. It shows the incoming panel wattage on the top left corner, the load wattage on the top right corner, the battery voltage on the bottom left corner, the charging current on the bottom right corner as well as a pictorial display of the battery charge state on the bottom center.

Overall I am satisfied with the performance and value of this charge controller. It free me from using multimeter to check the battery voltage many times a day, everyday.

Where can I buy them?

Now we know how to set up a small DIY Solar generator system and the type of solar panel, the next question will be where can we buy them in Singapore?

I have made many trips to Sim Lim Square and Sim Lim Tower during my lunch hours. At first I saw a 10W mono-crystalline panel selling for $50 in Sim Lim Tower. That works out to be $5 per watt which is way too expensive. I remembered reading from Internet that the price of solar cells has fallen from $4 per watt to $2 per watt. So I continued searching and came across one shop in Sim Lim Tower level three selling for $3.80 per watt. Still too expensive. I continued to search and found one shop at Sim Lim Tower level one selling their panel for $3 per watt. That was the lowest I can find in Sim Lim Tower and Sim Lim Square.

I almost bought the 90W panel from Sim Lim Tower at $270 until I came across a thread in Hardwarezone forum.




There was this guy, nick name Market98 selling the 30W mono-crystalline panel for $54 or $1.80 per watt. 

I later came to know him as Francis, a friendly and honest guy. He is operating from his fish/aquarium shop at No. 9 Pasir Ris Farmway 2, lot 35 block C Unit 3. (Opposite No.8). He opens daily from Noon to 6pm and Sat/Sun/PH: 9am to 6pm. You can contact him at Tel: 6581 6220. Pls call before you go there as sometime he is out running errant. 

Another guy I came across in Hardwarezone forum is by the nick name Tanericash. I think he is an hobbyist turn dealer. He was selling the 30W Poly-crystalline panel for $1.60 per watt. You can reach him by PM him in Hardwarezone forum. He also carries a standing DC fan which I am interest in.

So far, these are the 2 people that I think offer the best DIY solar min system in town. If you happen to come across even better deal, do drop me an email.

You can also explore ebay or Deal Extreme and purchase some of the component online. For Solar panel and battery, I think it is still better to purchase locally due to their weight and shipping charges.

I hope this will help you get started in experimenting with solar energy harvesting.
Do bookmark my blog and visit often and stay tune for future posting.
Cheers!

Types of Solar Panel - Which one should I get?

There are 3 main type of Solar panels based on their material. They are Mono-crystalline, Poly-crystalline and Amorphous Silicon (also know as thin film).

Of the 3, Amorphous Silicon panel is the most inefficient in converting sunlight energy into electrical energy. It requires a larger area to produce the same power as a mono or poly crystalline panel. It's believe to be between 2 to 3 time the size of crystalline panel. Because of the inefficient use of space which is limited for some of us staying in HDB flat, I do not recommend you use Amorphous Silicon panel unless you can make it into window panels to replace your existing window panels. But that will cost quite a lot.



Between Mono and Poly crystalline panels, the difference is quite small. Mono crystalline panel has slightly better performance than Poly crystalline panel but it is also slightly more expensive. At the time of writing, the Mono crystalline panel costs about S$1.80 per watt while the Poly crystalline panel costs about S$1,60 per watt.

Mono crystalline panel is made up of single type of crystalline. It is therefore more expensive to produced and cost more. It can be identify by the uniform color of the solar cells throughout the panel and has a diamond shape pattern in between the solar cells.



Poly crystalline panel are made up of many crystals of various size and shape forming a large block. The solar cells are then cut and slice from the big block of crystal. They are cheaper to produce than mono-crystalline cells and thus slightly cheaper for the same wattage it produced.

So between mono and poly, it all boils down to personal preference. I personally prefer the mono crystalline panel because of the uniform look and slightly better performance. But it's all up to individual, the difference is small.

Another important factor to consider is the size of the panel. Get one that can best fit into the area you want to mount the panels.