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.

Basic DIY Solar system setup

DIY solar system is actually quite simple. It is certainly not rocket science.
It consists of 4 basic components - Solar Panel, Charge controller, battery and voltage converter or Inverter which I will describe further below.

1st is the solar panel which is made of Photovoltaic (PV) cells. They come in different sizes and wattage or power.There are 3 main types of PV cells namely Mono-crystalline, Poly-crystalline and Amorphous Silicon also called "Thin Film".

Amorphous are those found on calculators and low power devices. They are not so effective and require more area/space to produce the same amount of energy as crystalline panel.

The differences of these 3 PV panels will be discussed in another post.




2nd is the solar charge controller. This is probably the most important component in the whole setup. It's function is to regulate the voltage from the solar panel to the battery. Without the charge controller, the panel voltage (which can be as high as 18V for a 12V system), will be too high for the battery (which is between about 10.8V to 13.4V max)  and will damage it. The charge controller also has a second function of preventing the battery from over discharge which again may damage the battery. So in summary, the charge controller protect the battery from over-voltage, over-charging and over-discharging damage. There are 2 main types of charge controller, namely PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking) which we will discuss in another post.

3rd is the battery. The battery or battery bank is a temporary storage for excess solar energy produce by the solar panels. It is called a bank because you deposit energy during the day and withdraw the energy for use during the night. There are different types of batteries designed for different purposes. The most common type use in small solar setup is the Sealed Lead Acid (SLA)battery. For a small DIY setup, we usually work on 12V. Just in case some do not know how much is 12Volts, we connect 8 AA batteries in series and we will get 12V (8x1.5V). This voltage is consider quite safe as it is low compare to our main 230Vac.



4th is the load or the output. Depending on the usage, a DC to DC (12V to 5V) converter is sufficient for most activity like charging your mobile phone, AA/AAA rechargeable batteries, powering 12V LED lights, 12V fans, rechargeable vacuum cleaner. If you plan to go higher level like powering household appliances which normally work on 230VAC, then you will need a 12VDC to 230VAC power inverter. Most on inverter will be covered in later post.

How to connect them?
All these components work on DC and have positive (red) and negative (black) indicate.
All you need to do is the learn how to strip wires and connect them using a test pen or screen driver. The charge controller is command center and all other components such as solar panel, battery and load are connected to the charge controller with positive and negative labelled.

Connect the battery first, negative follow by positive, then the panel and the load. Some controller has a button to turn off the power to the load, so you should turn it off before connecting the load.

I also place an in-line fuse between the positive terminal of the battery and the charge controller and another in-line fuse between the positive terminal of the load and the charge controller.
The fuses should be of the same rating as the output of the charge controller. This is to prevent accidental short circuit which may cause over heating and fire.

You may need cramping tool to cramp the wire to terminal connecters but this is not a must. You can always twist the wire around the terminals and use an electrical tape to cover the wire.

So, that's it, a simple setup to begin with and explore as you gain more knowledge. For a DIY project, it's always good to start small and expand later when you acquire more knowledge and experience.
I started with 30W panel, 10A PWM charge controller, 9Ah battery and a 12V to USB converter.
At the time of writing, I have 90W panel, 30A MPPT charge controller, 69Ah batteries, 2 DC to AC inverters and other gadgets. I use it to power my 26W solar fan and 6W 1 meter LED lights, charge my handphone and rechargeable batteries and other rechargeable gadgets.

Happy solar harvesting!

New to Solar Energy Harvesting

I was always fascinated by the ability to convert the energy from the sun to useable energy since young.
I was born in Singapore and stay here throughout my life. Singapore is located near the Equator and is an island country surrounded by sea. It is hot and humid throughout the year.

We have almost 12 hours of sunlight everyday and it is no wonder that many of us who stay in this country wish that we could make use of this abandon natural resource.

Solar panels and systems were very expensive in the past and out of reach for hobbyists like me. It was not until recent that the price of the solar panels has fallen below S$2 per watt that solar panels and small solar power systems become affordable. Now with as little as S$100, anyone can start playing with solar power harvesting.




My household utility bill has been increasing year by year. Recently my monthly bill exceeded S$200. My power supply portion alone accounted for more than 70%. My power usage shoots up from 300KWh per month to more than 500KWh per month, so I was thinking how to cut down my electrical bill. Then I happen to come across an interesting thread in Hardwarezone.sg/diy-solar-power-solutions forum.

It is an very interesting thread and contains lots of useful information for newbies like me. However, the thread is very long and took me many days to read through them. The information is also very scattered and un-organized. Therefore I hope to start this blog to organize the information to help those who are interested in starting a small DIY solar project.

So, stay tune for further updates!