MamboViewPoint solar 2th print solar.pdf · MamboViewPoint is an ecolodge the use of renewable...

____________________________________________________________________________________________________________________ MamboViewPoint a practical guide for using sustainable solar energy march 27th 2010 page 1 of 14

A practial guide for using sustainable Solar energy

October 7th 2011 Herman Erdtsieck, Director MamboViewPoint

MamboViewPoint

PO Box 157, Lushoto-Tanzania ℡ +255 78 5272150

[email protected]

www.MamboViewPoint.org

©MamboViewPoint 2010 Copying of this article or parts of it is allowed as long as it is accompanied with the acknowledgement and the website name www.MamboViewPoint.org


INS AND OUTS FROM THE MamboViewPoint SOLAR ENERGY INSTALLATION Introduction

MamboViewPoint is an ecolodge in the Usmabara Mountains in Tanzania. Since MamboViewPoint is an ecolodge the use of renewable energy is very inportant. Using solar energy is not rocket science but unfortunately there are some misty stories around which easaly can make a good desighn difficult. Below is extensivly explained how the MamboViewPoint solar installation is desighned and what are the important issues for using solar energy. The aim of this paper is to transfer our knowledge to everybody who wants to use solar energy. If you desighn it well you can have a lot of profit, using a small footprint only. Unfortunately the story is a bit technical. If you are not a technician, you just can read the yellow “what we have learned” boxes and believe us that it’s the truth.

Energy load The most important thing to start with is to consider the needed load. This has two different main issues:

1. Try to reduce the load as much as possible. 2. Try not to cover all your energy with solar but only the fair

part. Reduce the load The most important one is to use LED lightning. Nowadays there are nice LED lamps available which have as well a warm-white colour as well they fit in the regular fittings and have the regular voltage (230V). Also tube lights are available in LED. You just take out the starter from regular TL fittings and there you go. Also it is not always necessary to have that much light. A well considered plan for spotlights is better than some big lights for the whole place.

What you have to know before continuing to read: Solar energy is usable (but not very profitable) in countries with a lot of sun like in Tanzania but far less in cold countries like the northern part of Europe How sad that so many solar system are found in Europe and so few in Africa! In Europe those systems only are profitable because of heavily grant’s. Also in Africa they can’t compete with the regular electricity providers but they offer you a far more reliable and energy neutral system.


Table 1, comparison between power consumption of lights Watt Watt Watt Watt Saving (%) conventional 20 40 60 100 0 Energy saving 9 11 20 30 40 LED 1 2 3 5 95

Unfortunately in Tanzania there are hardly any reliable LED lights available. If they are they are from poor (Chinese) quality like so many technical products. Fridges take a lot of energy. Luck wise there are special “solar” fridges which are very economical (f.e. 30W for a 60 liter cooling box) They have an upper-door which is important because the cold stays inside when you open the fridge. They are also adaptable for use as freezer. Switch the lights on and off. Depending on human beings is not good enough because people forget to switch it off. There are affordable sensors which you can connect to lights in toilets, bathrooms and other rooms with temporally use only. Use timers to switch lights on places that need only light during the evening or the night. There are also light sensors but those are strange enough not widespread for sale and if they are, most the time expensive. Use netbook computers only. Especially the old second hand computers and monitors use a lot of power and most the time are not faster than the modern, affordable netbooks. Modern netbooks and LCD screens use less than 30Watts which safes 90% compared to the old computer-monsters. Outdoor you can use outdoor solar lamps with their own solar panels. The small ones are cheap available (unfortunately at least in rich countries). But the best are those who have a sensor. In the dark they burn small and when you pass they go bright. The best we found are sold by the German company Conrad.


Cover only the fair part of energy with solar Solar panels are still expensive. If you try to cover all your needs with solar the last 10 or 20% will make your installation extremely expensive because you have to calculate for the maximum use and those big users like water pumps and ovens only are used for a small part of the time. It’s better to get power for those big short period consumers from another source like the public grid or a generator. As long as solar panels and batteries are expensive this is the best solution. Unfortunately most solar suppliers are calculating with the maximum use, also because its in their interest to sell as many panels and batteries as possible. It’s the same during the rainy season. If you cover one week without sun this is fair enough. You are left with some generator-days a year, which is acceptable.

Voltage

Nowadays worldwide electricity is 230 Volt AC. (high voltage alternating current) Car electronics are 12V DC (low voltage direct current) This is an important detail because from both (230V AC and 12V DC) are a numerous number of equipment available. If you choose for any other voltage you will have trouble to connect and will need converters. If you use 12Volt, the equipment has to be close to the battery because you will lose a lot of energy in the lines and the lines has to be thick and are expensive. On a huge terrain like MamboViewPoint it would even be impossible to get the 12 volt to the other side of the terrain. For small installations 12 Volt DC will do and you can connect direct LED lights to the battery. But for a bit serious installation you will need an inverter which inverts the 12Volt DC from the batteries to 230V AC for the consuming equipment.

What we learned about the load: • Use LED lights only. • Use netbook computers only. • Don’t try to power the last 20%

also with solar. • Use solar fridges only. • Use timers and sensors to switch

the lights. • Don’t design for the maximum.


For big installations the problem with 12V is that you need a lot of current. For example a 1-Kilo-watt Load (which can be normal for a household) will give about 4 Amperes if you have a 230V installation but it will need about 80 Amperes when you have a 12V DC installation. This is one of the reasons that solar panels sometimes are joined together to make it a 48V or even 240V DC installation. The disadvantage however is that if you do so, you need special chargers and also can’t use the batteries for 12Volt loads anymore. Another thing is that the panels need to be all from the same wattage and if only one small part of one of the solar panels in is the shade or broken the rest of the panels don’t deliver the maximum current anymore. If you stick to 12 Volt this risk is far smaller since every solar panel works at its own and you can couple as many solar panels from different wattage as you want.

Solar panels

There are many different types of solar panels. Which ones to use and how to put them? Basically it does not matter which ones you take, as long as you take panels from the same wattage. However there is no need for this in a 12V installation, it’s handy because you can later change if desired and for making an array it’s more nice if they are all the same. Important is to know that solar panels work the best if they are put square to the sun. Since the sun is going from east to west everyday and from north to south and the other way around once a year you gain the most if you can turn them in both directions. This will give you at least 50% more energy than if you mount them in a fixed direction. In countries with high wages you can do this with automatically systems. Unfortunately those are a bit fragile and expensive so they can eat the profit totally. In low-wage countries you better turn them by hand for example by the watchman who is there all the time anyway. Earlier is stated already that a little bit of shade will reduce the power dramatically. That’s why it’s important that all your panels are in the sun as much as possible. There is no use to put an extra panel when only a piece of it is in the shade. Unfortunately the panels don’t or nearly work during night and when it is cloudy. (in contrast from what you often read as should panels deliver energy even when it’s cloudy, forget it.)

What we learned about the voltage: • Use 12 Volt solar panels and batteries only. • Only for small installations you can use 12V DC

else you need an inverter to 230V AC. • In case of a 12V installation the consumers must

be close to the batteries.


Batteries

The batteries for a solar installation are from a special type. This is because the charge and load is in contrast with a car battery a kind of steady. However it is possible, if you use a car battery like that it will not last long. If you use more batteries (what you most the time do with big installations) they must be all from the same type (Ampere-hour). Remind that it is not wise to add more batteries later because the new ones will not have the same specs like the old ones. Very important is never to unload batteries completely. If you do so it will be very difficult to charge it again and it can even damage the battery. The equipment on the load side has to be designed that it switches off when the voltage is to low. Unfortunately batteries don’t have a very long lifetime. This means that you have to replace them 2 or even 3 times within the lifetime of the solar panels. To calculate the number of batteries it is important to know that the loss of the batteries is depending on the time within they are charged or discharged. The loss is between 10% with currents till 5% of the capacity up to over 50% if you use currents over 30% of the capacity. So remind that you don’t get the same power out of it as you put into it.

What we learned about the batteries: • Always use special solar batteries. Car batteries

are working but will not last long. • Design the installation in that way that you don’t

need more batteries later. • Never unload batteries completely and use

equipment to protect total unload. • Charging and discharging always gives a loss.

This loss is dependant on the time within you charge or discharge. The faster you do the higher the loss. The loss can go over 50%(!)

What we learned about the solar panels: • Use solar panels of the same size and wattage. • Don’t put any part of the panels in the shade. • If possible make them rotating in 2 directions. • Afterwards you always can add more solar panels. • Don’t believe stories that solor panels deliver

energy during cloudy weather, they don’t.


Chargers To charge the batteries from the solar panels you need a charger between the panels and the battery. This can be one or more. To lower the current and also to spread the risk in case of damage it is better to make groups of solar panels all with their own charger. For small installations you can use a charger which is combined with a prevention for total unloading.

Inverter

To make 230 V AC out of 12V DC you need an inverter. This is an important part of the installation. There are different kind. The cheapest ones don’t make a nice alternating shape like you will get from the public grid. In that case you can get difficulties with some equipment which needs nice AC-shapes. The ultimate converter is the one which combines different functions: • Converting 12V DC from the battery to 230V AC. • Combining current from other sources like a

generator or the public grid with that from the solar installation.

• Charging the batteries from another source in case the solar panels are not enough (f.e. during longer periods of cloudy sky).

The Victron Phoenix is a converter like that and turned out to be very reliable. However other branches will have similar equipment but we don’t have experiences with them. The combination of solar power and an external source in very sophisticated and not obvious but at the same time a “killing application” You have to realize that the solar power has to synchronize with the external source before you can combine it. This has to happen without a current disconnection. With the Victron Phoenix it is even possible to limit the power which is provided from the external source which can be helpful if the external power source has a limit or if you don’t want to use external power because you want to favourite the solar power. If you use a combination like that you have to regulate the installation carefully because of the following reasons:

• If the external power is always available, the battery will be charged from there and you don’t use the solar panels anymore even if it’s sunny.

• During daytime the battery can be charged from the solar panels and from the external source. The total can exceed the maximum acceptable current.

What we learned about the chargers: • For small installation use a combined

charger / unload prevention. • For big installations use more

chargers, each with their own set of solar panels.


The best to think of is to regulate it in that way that the batteries are only charged from the external source if they are less than half full.

How to calculate the capacity from the solar panels and the batteries In annex 1 you find the calculation of MamboViewPoint. First the daily consumption is calculated which is in our case about 2Kwh. Than is calculated how many batteries are necessary to be able to survive for 6 days if the sun is not shining. This is about 12kWh which means there is a need of total 1 kAh batteries. (10 batteries of 200 Ah each, 1 kAh <kilo Ampere hour> = 12 kWh <kilo watt hour> with 12V) For one day consumption we need 6 panels of 65W. (this supposes the sun is fully shining for 6 hours and the efficiently of the panels is 65%) If we want to reload after a period of clouds in 6 days this needs another 7 panels. Remarks:

• Full sunny days are not many so recovering in general will take more than 7 days. • On the other hand full cloudy days are also seldom so till fully empty in general

will take more than 6 days. • If the batteries are full there is a not-used over capacity of 100%(!). • The over capacity will be reached after 8 full sunny days (6 for reloading 2 for the

daily use) in general it will take more days and in case of half-clouds even not be reached.

• Since we need the generator for the water pumps and the oven it’s running every day for about 2 hours. In periods of cloudy weather it can charge the batteries with 960Wh which extends the period till empty from 6 days till 9 days. In case of fully empty the generator has to run for 2 hours a day more which is still acceptable.

What we learned about the inverter: • There are two types of inverters. The cheapest one

does not make a nice current-shape which can be insufficient for some equipment.

• The ultimate inverter combines charging and a feed from the solar installation with another source like a generator.

• It is important to adjust the inverter carfully to get the maximum profit.


Thunder and emergency lights Al kind of nasty things can happen: Thunder can threaten equipment and lights, clouds can appear for weeks, generators can brake down and of course those things are happening preferable at the same time. MamboViewPoint is situated on the top of a 1900 m high mountain. Also a preferable place for lightning to strike. Despite of all kind of over voltage protection there is only one good solution to reduce the threat and that is to place sockets everywhere and to unplug those during thunderstorms. In this way the whole electrical installation is divided is small islands and if the thunder hits only one island is struck. Unfortunately if you unplug the lines no more electricity is provided. Here there is a good solution to provide at least some light during thunder and failing of the main installation. Place in every house a small 20W solar panel with a 27Ah battery and some small 12V LED lights. If those lights are 2 Watt it will last for 150 hours or with a use of 4 hours a day for one month! You can use the lights also under normal conditions. If required you put some more lights and a battery with a little more capacity. Other important equipment like fridges can have their own panels and batteries as well. In this case during thunder and emergency only power on the sockets is missing. You can add some 12 phone chargers if required.

What we learned about designing: • The capacity of the batteries is depending of

the consumption and how many days without sun you want to survive.

• The number of panels is depending of in how many days you want to recover after cloudy days. If you choose too much panels you create an unused overcapacity.

• To reduce costs and over capacity it’s fair to support with an external power source in case of more cloudy days on a row.

What we learned about thunder and emergancy: • Provide small 12V LED lights with separate batteries and

small panels. • Unplug the main grid on several places to divide the

installation in small islands.


Financial profits and losses

If you buy a solar installation because you think it’s cheaper, forget it, it’s not. Even in good conditions you will not gain enough energy to make it profitable. Unfortunately the solar panels are way to expensive. In western countries only because of heavily grants people have some small profit, but if you don’t have grants the public grid is cheaper. Below you find the calculation which shows that solar energy is about twice as expensive as the public grid.

MamboViewPoint solar Break down for 20 years Investment € 10,000 Maintenance € 2,000 Battery replacement € 6,000 total € 18,000 Gained energy 24,000 kWh costs Solar € 0.75 per kWh costs generator € 0.75 per kWh Costs public grid € 0.30 per kWh

Why should you us solar power if it’s that expensive? If you are in a remote area without public facilities, there is no choice and it’s cheaper (and way more silent) than a generator. If there is a public source, you will notice that the public grid in development countries often is not reliable, and if they have power it can be of a very bad quality. Especially the combination of both can make your installation very reliable with a constant voltage. If you have a public grid you even can reduce the capacity of the solar system just to make it reliable.


Experiences with the MamboViewPoint solar installation

The installation like it is described in this paper showed to be very reliable, After one year use the only power interruptions has been because of maintenance and extension. This even made people jealous who have to face the constant power interruptions of the local power provider Tanesco. Remind in Mambo there is no public electricity at all, but the economics in small towns like Lushoto often burden heavily because there is no electricity during parts of the day or sometimes even during some days on a row. (or like recent in Zanibar for some months) Keeping an eye on the system It is very important to keep an eye on the system, what is your use and what are your profits. Also you can prevent a power cut if the batteries are nearly empty by charging from the generator in time. For this you need the following additional equipment:

• A kilo-Watt-hour meter • A battery monitor for the left capacity and the momentary load or charge • On the chargers a display for the delivered power and the momentary profit. • A mobile powermeter to measure the use of the individual lamps or other users.

Postscript:

However we tried to be complete, some things can be wrong or incomplete. We appreciate to get commands so we can improve this document. Feel free to send your comments to [email protected]

What we learned about the costs: • Solar energy is more expensive as energy

from the public grid. • In countries like Tanzania solar energy is way

more reliable than the public grid, especially when you combine it with the public grid.

• If you don’t have a connection to the public grid there is no choice.

What we learned about the experience: • Solar energy can be very reliable. • You need some measure equipment to keep

track of the behaviour. • It needs daily attention to turn the panels in

the sun and to see if extra charging is needed.


Annex 1 Calculation of the needed number of batteries and solar panels for MamboViewPoint

estimated number of solar panels effective capicity to cover 1 day use 2,086 Wh / day charging during 6 hours 348 W / hr efficiency 65% total needed capacity 535 Whr

total number of panels 85W 6per day consumption

total capacity to reload in 6 days 348 total number of panels for reloading 7 total number of panels 13

estimated energy consumption nmbr what power

(w) hours/

day total power

consumption (wh)

unit

20 LED 3 4 240 30 LED 3 1 90

2 Tube LED lights 16 4 128 8 Tube LED lights 16 1 128 2 netbooks 30 10 600 2 netbooks 30 2 120 1 printer 300 1 300 2 fridge 30 8 480

total 2,086 Wh/day estimated battery capacity

6 days full power consumption 12,516 Wh operating on 12 V 1,043 Ah


Annex 2 Block diagrams Below the block diagrams of the MamboViewPoint solar installation and a small installation (which we use for the luxury tents)


Annex 3: Equipment

Purpose Equipment Supplier Why that supplier

Remarks

Small solar panels 20 Watt Rex investments Dar es Salaam

The first shop we found for the first need

Charger / protector for the small installation

Morningstar SHS-10 (10A)

Ensol Dar es Salaam Various suppliers sell this

Simple and reliable

Big solar panels Cristalline 85 watt Ensol Dar es Salaam Reliable supplier who sells also Victron equipment

Solar chargers Morningstar tristar TS60 (60 A) incl display

Ensol Dar es Salaam Panel is for keeping track of the performance of the solar panels

Inverter Victron Phoenix multiplus 12-1600-75

Stroomwerk / Victron the Netherlands (also available from Ensol)

We tested it in the Netherlands during preparation of the project

Victron gives a very good service also on distance

Batteries Solar Gel 10 x 200 Ah

Ensol, Dar es Salaam

Take care that all the connections are included in the delivery

Generator Kipor 5kW petrol Webshop in the Netherlands

We tested it in the Netherlands during preparation of the project

We had some problems with the starting engine. For the rest it’s has a good performance

Safety guard AVS30 Solltec Ensol, Dar es Salaam

Protects the inverter for bad power from other sources.

Battery tester Xantrex battery status monitor TM500A

Ensol, Dar es Salaam

Disadvantage that the status gets lost when it’s disconnected.

Outside lights LED lights (garden and floodlights)

Conrad, Germany They were the only ones who sell those for a affordable price

Those lights have their own panels and a moving-sensor.

12 LED lights and Ikea Very suitable for 12V installations

230V LED design bedside lights

Ikea Very nice but expansive lights

230V LED spotlights WW-3-E27-3x1W-220 Led-line the Netherlands

Web-shop Too many stop working far too soon

230 V LED lamps 1-LED Kogelkoplamp 220V - E27 COOL WIT

Led-line the Netherlands

Very nice in outdoor ball-fittings

Computers Acer one Netbook Some web-shop in the Netherlands

Most cheap Don’t forget to tie them. (there are special expensive locks available)

Fridges Aeca Solar fridges 60l Prevent Germany webshop Very low energy consumption. Upper door is not handy.

Windmill Air-X 300W Webshop the Netherlands

Webshop (not excisting anymore) but also in Tanzania available

Reliable windmill

MamboViewPoint solar 2th print solar.pdf · MamboViewPoint is an ecolodge the use of renewable...

Documents

Transcript of MamboViewPoint solar 2th print solar.pdf · MamboViewPoint is an ecolodge the use of renewable...