Solar Thermal Panels and Heat Pumps Hybrid Systems

Figure 1

The addition of solar thermal panels in conjunction with Heat Pumps to form a hybrid system certainly does have the capability of creating a complete energy efficient solution for any hot water installation regardless of volume requirements.   Solar thermal panels will contribute their maximum free “solar” energy only during the daylight hours when the sun is shining brightly and without any cloud cover.   Air to water Heat Pumps on the other hand will continue to contribute free “solar generated” energy from the air during the daytime, rainy or cloudy periods, as well as night time.  Another point to consider is that air to water Heat Pumps will operate at optimum efficiency and therefore contribute the maximum level of free “solar generated” energy during the same periods of the day as the solar thermal panels which is, during the highest ambient temperature periods of each day.   Therefore when solar thermal panels are used in conjunction with Heat Pumps in a hybrid system the “actual” achievable saving in energy will be reduced because both systems enjoy a “positive” COP.  When the Solar thermal panels are contributing the maximum amount of free “solar” energy, the Heat Pumps will also be contributing the maximum amount of free “solar generated” energy from the air.

Figure 1: above shows a typical layout with solar thermal panels connected with Heat pumps. The daily energy contributed by solar thermal panels can be calculated by using the following formula:

kW = Collector area x Collector efficiency x Average Daily Radiation (Mj/m²) ÷ 3.6

Figure 2

In addition, solar thermal panels actually lose efficiency as the water temperature rises as shown in the chart - Figure 2.  For a good quality solar thermal panel operating in the highest instantaneous solar radiation conditions it can be seen that the efficiency at a point where the temperature difference between the solar panel and the ambient temperature is around 30 degrees Celsius the efficiency is approximately 75%.  If we select as an example the average daily radiation of 17.56 Mj/m² per day for Manila Philippines the equation would be:

 kW      = 1m² x 0.75 x 17.56 Mj/m² ÷ 3.6

            = 3.66 kW/m² per day of available solar collector aperture area.

Therefore, during the maximum energy collection period for the solar thermal panels they will contribute approximately 3.66 kW of energy for every one square metre of collector aperture area that is installed.  In the same location (Manila - Philippines) during the same period & same climatic conditions that has been used to assess the solar thermal panels, the Heat Pumps would also be operating efficiently and producing a COP of approximately 3.8 to 4. 
Then assuming that the solar collector panels were NOT installed as part of the hybrid system and only the Heat Pumps were required to contribute the total energy requirement during that same period.  The 3.66 kW/m² per day of “free” energy contributed by the solar thermal panels would only require approximately 0.96 kW of energy to be “consumed” by the Heat Pump to produce 3.66 kW of output using a COP of 3.8 for the Heat Pumps.  However, in the location of Manila – Philippines during the peak high ambient temperature periods the COP for the Heat Pumps may even be around 4 of higher which would result in even less energy to be “consumed” in order to produce 3.66 kW of heating output.  Therefore, the lower calculated energy consumption, for the Heat Pumps that would be required to produce the same heating output as the solar thermal panels becomes the “actual” or real amount of energy saving that should be used to calculate the ROI or payback in relation to the cost of supplying and installing the solar thermal panels in a hybrid system with Heat Pumps.

By: Mel Peatey.

Metran Swimming Pool Heat Pumps

The Air to Water Metran Swimming Pool Heat Pumps are available in both vertical and horizontal air discharge options.   Depending upon the installation location there are also options for the outer casings of the Swimming Pool Heat Pumps namely; powder coated steel, UV stabilized ABS or stainless steel.   The main feature or “heart” of the Metran Swimming Pool Heat Pump is the patented titanium heat exchanger.  Without an effective and durable heat exchanger a swimming pool heat pump will become ineffective in a very short period of time due to the rapid deterioration of incompatible components.  For example; the advantage of the titanium heat exchanger over a cuprous nickel alloy heat exchanger is that it is not susceptible to the highly corrosive chemicals (particularly high levels of chlorine) that are generally present in all swimming pools and spas.  The external casing component of the titanium heat exchanger is a fully molded non-corrosive, high impact strength material that can withstand high water pressures as well to ensure durability and maximum performance of the complete Metran Swimming Pool Heat Pump at all times.

Scroll compressors are used because they have 50% fewer moving parts than standard piston type compressors. This equates to greatly improved reliability and improved efficiency as well as reducing noise levels to a minimum.   The Digitally-based microprocessor can control water temperature to within 1ºC of the set point.  The controller also permits the user to pre-set different pool and spa water temperatures and it can also prevent unauthorized tampering by the use of locking controls via a Celsius control key.  The versatility of the Metran Swimming Pool Heat Pump is again demonstrated by its capability to heat and cool a swimming pool or spa in different climatic conditions.  This allows the operator to have full control all year round.   The Metran Swimming Pool Heat Pump can warm your pool or spa with the reliability and efficiency of our other heat pumps, but with the flip of a switch, it can also cool your pool or spa to refreshing temperatures during hot summer months. For cooler climates, heating & cooling heat pumps offer unique advantages over the passive defrost models.

The Metran Swimming Pool Heat Pumps are also hot gas defrost heat pumps that are uniquely equipped for an active defrost cycle.   Active defrost involves directing hot refrigerant vapor to the heat collector thereby melting accumulated ice away in a matter of a few minutes and then allowing the heat pump to return back to normal heating cycle.  Standard defrost heat pumps may remain off for extended periods when defrosting during very cold weather.  However, because of the hot gas defrost function on the Metran Swimming Pool Heat Pump it has the ability to continue to operate-even during freezing weather.  Hot gas defrost models will extend the swimming season longer than any standard-defrost heat pump.  A large variety of Models are available ranging from 4 kW heating output right through to 149 kW heating output which will ensure a suitably sized product can be selected from the calculation chart for any project.

By Mel Peatey

Solar Lantern Lighting Kit

The Solar Powered Lantern is a lighting system that consists of 28pieces including an LED lamp, battery and controller all placed in a strong metallic housing and ABS plastic as well as a solar panel and a AC/DC adapter.  The battery is charged by two methods:
1.    By electricity generated through the solar panel
2.    By the AC/DC Adapter that is supplied with the kit.
The lantern is basically a portable lighting device suitable for either indoor or outdoor lighting covering a full range of 360 degrees.
The product features adjustable lighting modes where the setting can be “strong” to an “energy saving” setting   The “energy saving” setting has a brightness of approximately half the maximum brightness strength but this setting will allow the lights to operate for a longer period during the night time.
In addition, there is a DC output for mobile phone charging, which is suitable for any type mobile phone. The complete unit is compact and light weight, as well as being easy and convenient to use.

The product is suitable for outdoor campers, hunters, hikers, boat cabin lighting, vehicle roadside emergency lighting, recreational vehicle cabin lighting, earthquakes and hurricane emergency kits.  Indoor applications include home lighting in rural regions where the power supply is irregular or scarce and also in urban areas as backup lighting during power cuts as well as for mobile phone charging during these periods.

By Mel Peatey

Solar Home Power Supply System Model No.: SHS1206

This great new addition to the range of solar lighting kits now allows you to create a power solution to match your requirements.  Each system includes the solar panel, charge controller, solar battery, DC to AC inverter, cables & DC 12V lamps to complete your system.
The Model SHS1206 - 6W Solar lighting Kit gives you all the components needed to install a small lighting system in remote homes, caravans or wherever you need a reliable power source for lighting.

This Solar Lighting System consists of 3 LED lights & mobile phone charger as shown in the illustration.  The PV Solar panel has a maximum generating capacity of 6W and has an expected life cycle of approximately 10 years.   The three lights that are supplied with the Model SHS1206 consist of 2 pieces of 12V/3W LED bulbs and 1 x 12V/1W LED bulb.  The controller incorporates over-charging (14V) and over-discharging (10.5V) protection functions as well as short-circuits protection.  The battery is a 12V-4AH lead-acid battery with a rated charging current of 1Amp and a rated discharging current of 2Amps.

There is a no load loss of 8mA and a USB port current of 500mA.   The estimated full charging time with the solar panel is ten hours when clear sunny conditions are available.   Orientation of the 6V Solar PV panel in a direction facing towards the equator (North for Southern Hemisphere Countries and South for Northern Hemisphere Countries) will ensure maximum collection of solar energy each day.
An approximate lighting duration after the battery is fully charged of around 5 hours when the 3 lights are operated at the same time can be expected.

By Mel Peatey

Low Cost Solar Lighting Kits

In remote Regions of Developing Countries the people tend to use the traditional methods of either burning firewood, lighting candles or kerosene lanterns in order to provide lighting during the night time periods.  It is well known that candles and kerosene are expensive for these people as well as being harmful to the eyes - particularly when children are exposed to these types of lighting.   In addition, gathering firewood is heavy, hard work that is generally carried out by the women and sometimes the children of these communities and burning firewood can contribute to larger rural fires that can destroy large areas of vegetation.  Burning firewood is also not really environmentally responsible and could be considered to be somewhat of an unsustainable resource.  In many cases the remote Regions in Asia, Pacific Islands, and Africa are blessed with abundant amounts of solar energy which is freely available but is very much underutilized.  In order to overcome the problems with traditional lighting methods there has been a concerted effort to develop low cost, but effective solar lighting systems for these Regions.   The benefits of using the low cost solar lighting kits is that they are easy to install, are safe to handle, and simple to operate.  The solar PV lighting kits generate direct (DC) current which is totally safe to use unlike alternating current (AC) that is used in most developed world locations.   A NI-MH (Nickel Metal Hydride) rechargeable battery is used instead of lead-acid battery or NI-CD battery because of its long life, no memory effect, non-toxic, and is environmentally friendly.  Once the kit is installed, the sun will provide the energy needed to operate one 6V/1W LED lamp that is supplied with the Model SRY-001E (as illustrated above) for up to 8 hours after the battery is fully charged.   The expected life cycle of the Model SRY-001E lighting kit is approximately 10 years.  Over charging and discharging protection devices are incorporated into these lighting kits to simplify the use of the products.  Additional charging points are also available for other devices such as mobile phones.
 
Since the year 2009 over 100,000 pieces of the Model SRY-001E Lighting Kits have been installed in various parts of Africa and another 20,000 units have been sent to remote locations in South America.  The World Bank has recently conducted quality testing for the Model SRY-001E product and it has now been passed and has been accepted for their "Lighting Africa" Solar program.
There are a number of different Solar lighting kit models available in the range that are CE accredited and also include extra LED lamps and other charging options.  These kits have slightly larger solar panels that are capable of collecting the additional solar energy that is necessary to power the extra lights or charging points. 
 
By Mel Peatey

Solar Thermal Collectors Connected to Heat Pumps

There can be some advantages gained by connecting Solar Thermal Collectors to Heat Pump water heaters, but there are some important points to assess before this combination can be recommended.  The first point to consider is the economics of the project.   In other words will the addition of Solar Thermal Panels provide sufficient reduction in traditional energy use, which can then be calculated as a cost reduction when compared to the actual initial cost of supplying and fitting the Solar Thermal Collector Panels?

                                                              Schematic Image Only

There is an unwritten expectation for energy efficient products such as Solar Thermal and Heat Pump systems to provide a reasonable “payback” period, and this can sometimes be linked to the expected life cycle of the system or probably more closely linked to the warranty period offered for the products involved.   If the capital cost can be recovered within the warranty period then it is worth being given further consideration. However, when assessing the value of adding Solar Thermal Collector Panels to a Heat Pump installation it must also be remembered that during the daylight hours when the Solar Thermal Collector Panels could be contributing to the energy input of the system, that is also the period of each day that the Heat Pump units would be operating at their highest efficiency as well so the amount of purchased (input) energy for the Heat Pump units during the day time period could be between 3½ to 4.0 times less than the actual output that is produced in the form of hot water depending upon geographical location, ambient temperature and humidity.

The thermal contribution to a Heat Pump system from Solar Thermal Collector Panels is governed by the amount of radiation that is available at any given time and this can be intermittent because of varying weather conditions.   Therefore it is important to recognize that the Heat Pump units must be considered as the primary heat source and sized accordingly to be able to meet the total hot water requirement of the project due to the reliability of Heat Pumps being able to produce energy efficient hot water in all conditions including daytime, night time, as well as cloudy or rainy periods.  The Solar Thermal collectors will therefore only provide supplementary energy input during periods when there is a favorable level of radiation available for collection.  A number of factors can influence the decision to add Solar Thermal Collectors to a Heat Pump installation or not, but generally it has been found that in Regions where Government or Utility incentives are offered for the inclusion of Solar Thermal Collector Panels and the value of that incentive covers the cost of the Solar Thermal Collector Panels then obviously the economic equation is positive however, when no incentives or subsidies are available then there are some questions that need to be asked as to the added value of the Solar Thermal Collector Panels fitted to Heat Pump Units.

By Mel Peatey

Water to Water Heat Pumps

Another option for Commercial/Industrial Heat Pump water heaters is the Water to Water - or hydro sourced Heat Pump.   Water source heat pumps (WSHP) are specialized types of heat pumps that can also be used as reverse cycle or multi function units that use water as a heat source when in the heating mode and as a heat sink in the cooling mode. In the Water to Water HeatPump, heat is absorbed or rejected in a fluid medium rather than from the ambient air. Water loop heat pumps (WLHP) use a circulating water loop which could be from a chiller/cooling tower system as the primary heat source for the liquid refrigerant causing it to vaporize before moving it to where it is upgraded by an electrically-driven compressor and is then subsequently delivered at a useful super heated temperature for heating potable water via a suitable heat exchanger.

A typical schematic of a multi function Water sourced Heat Pump shown above indicates how in some cases a single Water to Water Heat Pump Unit can be used to provide hot water, air conditioning, as well as under floor heating if required.   In the schematic layout above the primary heat source can be provided by any medium (ground, lake, sea water or hotel cooling tower circuits) where heat energy can be captured (transferred) in the primary evaporator in the Heat Pump Unit.   These types of Heat Pumps can also be used very effectively for just the hot water output function depending upon the project requirements and still have the capability of delivering a very high Coefficient of Performance (COP) outcome of over 370% more than the actual energy consumed.   However, when used as a multi function unit for example, delivering hot water and air conditioning in an ambient temperature environment of around 24ºC the combined COP’s for both functions can be as high as 700% more than the energy consumed for the operation of the system.

By Mel Peatey.