500-600 paper

Energy Conversion and Management 51 (2010) 1621–1628

Contents lists available at ScienceDirect

Energy Conversion and Management

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e n c o n m a n

Economical investigation of an integrated boiler–solar energy saving system in Jordan

A. Al-Salaymeh a,*, I. Al-Rawabdeh b, S. Emran c,1

a Mechanical Engineering Department, Faculty of Engineering and Technology, University of Jordan, Amman 11942, Jordan b Industrial Engineering Department, Faculty of Engineering and Technology, University of Jordan, Amman 11942, Jordan c Euro Boilers Company, Middle East Est. For Heating Equipment Trade & Industry, P.O. Box 310038, Amman 11131, Jordan

a r t i c l e i n f o a b s t r a c t

Article history: Available online 6 January 2010

Keywords: Solar energy Energy saving system Space heating system

0196-8904/$ - see front matter � 2009 Elsevier Ltd. A doi:10.1016/j.enconman.2009.08.040

* Corresponding author. Tel.: +962 6 53 55 000x27 E-mail addresses: [email protected] (A. Al-Salay

Al-Rawabdeh), [email protected] (S. Emran). 1 Tel.: +962 6 4894586; fax: +962 6 4888049.

Jordan is relatively poor in conventional energy resources and is basically a non-oil producing country, i.e. its energy supply relies to a very large extent on imports. It is therefore unlikely that any future energy scenario for Jordan will not include a significant proportion of its energy to come from renewable sources such as solar energy. The lack of an integrated energy saving system which utilizes the solar energy for domestic hot water as well as for building space heating was the main motivation for the present study. In Jordan, there is no existing system can provide the integration mechanisms of solar energy and fuel combustion with electrical ones. Also adding new and related products increases sales of current boilers products and can be offered at competitive prices.

During our investigations, it has been found that the market demand for boiler–solar integration sys- tem in terms of the system acceptability, system feasibility, and system values is very high especially after the increased in oil prices during the last 3 years, i.e. 2006–2008. The market trend shows that even though solar collector is not attractive as an energy source for domestic hot water, but the combined sys- tem for space heating and domestic hot water is fully accepted. However, the market demand for such a system is not completely identified yet but the awareness and the discussion of the idea shows a good potential.

The economical study about the integration system of boiler and solar energy shows that using solar water heaters to heat space and for domestic water is cost-effective. Payback can be as low as 3 years, and utility bills are much lower than they would be using a conventional heating system. The initial draft and design of a prototype for the boiler–solar–electrical integration system has been carried out.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction coming 5 years, e.g. Al-Salaymeh [2]. The Jordanian authority and

One of the most important energy sources in our economy is still oil, which is not renewable considering our lifetime. Jordan is an energy importing country; about 96% of its energy needs sup- plied from abroad as crude oil and refined products. Hrayshat and Al-Soud [1] pointed out that the share of solar energy in the total energy mix in Jordan is estimated to be around 1.7% during the year 2002. They also showed that the expected share of solar en- ergy in the total energy mix in the year 2007 is estimated to be around 2.1%. During the Renewable Energy International Confer- ence which was held in Bonn, Germany during 1–4 June 2004, Jor- danian authority has been committed to have 5% of its total energy requirements from renewable energy resources for the next

ll rights reserved.

88; fax: +962 6 53 555 88. meh), [email protected] (I.

especially the ministry of Energy are working currently to have 7% of the total energy requirements in Jordan to be from renewable energy resources in 2015 and 10% in 2020. The share of renewable energy in the primary energy supply of the southern Mediterra- nean countries has been relatively low and varies from a minimum of 0.6% in Tunisia to a maximum of 19% in Palestine. This share can reach 2.0% in Algeria, 2.8% in Lebanon, 4.4% in Egypt, and 6.5% in Syria.

In fact, Jordan is blessed with huge amounts of renewable en- ergy resources, particularly solar energy. In order to reduce depen- dence on the imported oil, Jordan has pursued programs for promoting solar energy involving systematic monitoring and assessment of technological developments combined with the implementation of appropriate technologies, demonstrations and pilot projects [3–7]. The current tendency in Jordan is to use in fu- ture various solar energy applications in the over all mix of energy in Jordan, as well as identifying potential areas for utilizing future technologies and recommending future courses of action to encourage the commercial utilization of solar energy technologies.

1622 A. Al-Salaymeh et al. / Energy Conversion and Management 51 (2010) 1621–1628

As we know, all sources of energy may be grouped into two gen- eral categories; income energy, which is the energy reaching the earth from outer space such as solar energy, and capital energy, which is the energy that already exists on or within the earth such as fossil fuels, e.g. [8]. The hot Sun gives light and life and it is an inexhaustible supply of pollution-free power. The ancient Egyptian Pharaohs solar heated their palaces by capturing solar energy in black pools of water by day and draining the hot water into pipes in the floor of the palaces at night. Affluent ancient Greeks de- signed their homes orientated to the sun to use winter sunlight for heating. Large south-facing windows were used to collect solar heat, which was stored in massive walls and floors for gradual re- lease throughout the night. Solar energy put to full use would help to give the world energy independence, minimizing dangerous pol- lution levels and our dependence on fossil fuels. Therefore, solar energy can be considered as the most abundant continuing source of energy available to the human race.

One of the promising usages of renewable energy technology is the installation of the solar collector system, which has already demonstrated its effectiveness and holds great promise for hot water generation. The applications of the solar collector system have become more widespread in both developed and developing countries [9,10]. Due to high and reliable solar irradiance of about 5.5 kW h/m2 day a domestic usage for solar energy in Jordan over the life time has the potential to produce a domestic hot water in addition to the heating and cooling of buildings for about 330 sunny days per year using solar collectors [11]. Solar irradi- ance varies with season and time of the day due to the various Sun positions under the unpredictable weather conditions [12]. Conventionally, different mathematical models have been devel- oped in Europe to predict the solar irradiance on various in- clined-surfaces using horizontal data [13,14]. Data on average hours of sunshine or average percentage of possible sunshine hours are widely available from stations in many countries, e.g. [15]. Al-Salaymeh [2] developed a mathematical model for the pre- diction of global daily solar radiation on horizontal surfaces for Amman city in Jordan.

2. Aim of the work

The price of oil is increasing and the energy bill is very expen- sive for Jordan. As it is known, Jordan is imported oil from neigh- boring countries and this oil costs too much. Currently, a local study on renewable energy reported that solar technologies are potentially suitable for wide scale applications in Jordan. These re- sults show that Jordan need to begin to rely more on solar energy in order to reduce the dependence on imported expensive sources of energy. The energy demand, in Jordan, was doubled during the last 20 years, and expected to continue at the same rate. Hence, all recent energy forecast scenarios showed that the national con- sumption might double between 2015 and 2020. Due to increasing oil prices, the financial aspect of this problem has increased and its resultant outcomes are clearly observable these days in Jordan.

Utilizing of solar energy with boiler systems for domestic hot water as well as for building space heating can save energy and therefore can reduce the energy cost for domestic uses. The idea shows that a significant market segment is willing to invest in this system mainly to the expected increase in the fuel cost. The market trend shows that even though solar collector is not attractive as an energy source for domestic hot water, the idea of the integration is fully accepted and it needs to be tested on real cases.

The present investigation aims to develop a new energy saving system that integrates solar, boiler, and electrical systems for heat- ing purposes. The draft of the initial features and characteristics of the system is shown in Fig. 1. The system pilot testing includes

offering the idea of the system to a sample group of customers to determine if these customers need the system and are willing to buy it, identifying if there is a demand for the new system, whether modifications or changes to the terms and conditions will make the system more appealing, and what features or processes need adjustment, and calculating the cost and price of the system. The proposed methodology based on the economical study about the integration system of boiler and solar energy.

3. Theoretical background

Energy is one of the most important factors in wealth genera- tion, economic growth and social developments of the present countries. Based on historical data, one can observe that there is a strong relationship between the development of economic activ- ities and availability of energy resources, i.e. energy is of vital importance all over the world for the process of production and manufacturing, and as such, a key element of sustainable develop- ment of countries.

Referring to the measurements on radiation as well as to the variation in the topography and climatology of Jordan, the country is divided into five regions [16–18].

1. The southern region (29–30.5 �N, 35–38 �E): in this region, the annual daily average values of global irradiance are between 6 and 7 kW h/m2 day.

2. The eastern region (30.5–32.5 �N, 36.5–39 �E): in this region, the annual daily average values for global of about 5.0 kW h/ m2.

3. The middle region (30.5–32 �N, 35.5–36.5 �E): in this region, the global irradiance is about 4.5 kW h/m2 day in this region.

4. The northern region (32–33 �N, 35.5–36.5 �E): in this region the annual daily average value of global irradiance is about 5.5 kW h/m2 day.

5. The western region (30.5–33 �N, 35–35.5 �E): in this region, the annual daily average values of global irradiance are between 4.5 and 5 kW h/m2 day.

In general, the abundance of solar energy in Jordan is evident from the annual daily average of global solar irradiance, which ranges between 5 and 7 kW h/m2 day on horizontal surfaces. This corresponds to a total annual value of 1600–2300 kW h/m2 year. The measurements data that including horizontal solar irradiance and sunshine duration of solar irradiance for Amman city (latitude of 32�10N) has been taken. Al-Salaymeh [2] predicated global solar radiation data on a horizontal surface for Amman city as shown in Fig. 2. The scatter in the data shown in Fig. 2 is due to low number of years that is used in the calculation (only 3 years).

Different correlation formulas for global solar radiation for Am- man city that used the Sine wave correlation formula with con- stant Y-value, Lorentzian correlation formula, Gaussian correlation formula and the 4th order polynomial degree are shown also in Fig. 2, e.g. Al-Salaymeh [2]. The mean value of energy of quasiglobal radiation for Amman equals 5324 kW h/m2 day. Jor- dan receives the most solar energy in June (mean value 7995 kW h/ m2) and the least in December (mean value 2676 kW h/m2).

Fig. 3 shows the meteorological data for sunshine duration in Amman which acquired from observed mean values on meteoro- logical stations for 3 years. The scattering in the data is very high because the number of years used to calculate the average sun- shine duration is only 3 years. The maximum value of sunshine duration in Amman occurs in June and July (mean value is 11.86 h for June and 12.05 h for July) and the least in December (mean value 5.14 h), e.g. Al-Salaymeh (2006).

Solar collector

Boiler Electrical heater

Hot Water Temperature Heating load

Computer aided controller (PLC-

Based)

Water Feed Rate

Ambient Temperature

Heating Capacity Heating Capacity

Solar Intensity

Fig. 1. The initial features and characteristics of the boiler–solar–electrical integration system.

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Fig. 2. Global daily solar radiation data with different suggested prediction models in Amman, Jordan as a function of time.

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1624 A. Al-Salaymeh et al. / Energy Conversion and Management 51 (2010) 1621–1628

3.1. Collector thermal performance

The thermal performance of a solar collector is determined by establishing an efficiency curve from the instantaneous efficiencies obtained using a combination of values of incident solar radiation, ambient temperature, and inlet fluid temperature. Measurements should be made for the fluid flow rate, the temperature of the fluid at the inlet and outlet, the incident solar radiation, the ambient temperature, and the wind speed.

g ¼ Useful Energy Collected

Incident Solar Energy ¼

Q u I A

ð1Þ

where Q u ¼ _m CpðT o � T iÞ, _m is the mass flow rate, Cp is the specific heat, To is the temperature of the fluid leaving collector, Ti is the temperature of the fluid entering collector, I is the incident solar en- ergy per unit area and A is the area of the collector.

Due to the inevitable changes in solar irradiance and to exclude time dependencies, integration and averaging over a period of measurements is required. Eq. (1) can be rewritten as:

g ¼ R t2

t1 m � cp � ðT o � T iÞ � dt

A � R t2

t1 I � dt

ð2Þ

The percentage of energy saving in the case of a combined so- lar–boiler energy saving system can be calculated as the following:

% of saved energy ¼ heat gained from collector

boiler input energy ð3Þ

The calculation of the amount of fuel consumption in each month by using the conventional boiler system for space heating has been carried out by using the degree day method, e.g. Hammad and AlSaad [19].

4. Design of energy saving system

Solar energy is a renewable resource that is environmentally friendly and it can be used in many ways for water heating and space heating in buildings. The integrated system will reduce the need for conventional water heating for domestic usage as well as for space heating, minimizing the expense of electricity or fossil fuel to heat the water and reducing the associated environmental impacts.

By using passive solar systems or active solar systems or a com- bination of both, solar energy can help heat or cool buildings. Incorporating passive solar designs can reduce heating bills by as much as 50%, e.g. [20]. In the space heating, it is recommended to use flat-plate collectors which can heat the water temperature till 80 �C. Also, evacuated-tube or heat-pipe collectors can be used to obtain a high water temperature and a high efficiency especially in the winter season. Currently, evacuated-tube collectors are proved to be more efficient than flat-plate solar collectors because the efficiency of flat-plate solar collector decreases as the ambient temperature decrease and it might be to reach zero at cold condi- tions. The evacuated-tubes collectors have a high value of effi- ciency and it can save more than 90% from the heating energy bill.

Using solar water heaters to heat building is cost-effective. Of course, inside buildings generally will have a conventional heater or boiler as back-up. When the space needs heating, water is di- verted to the collectors, where it is warmed and returned to the building.

The solar integrated system is a solar thermal system that can provide domestic water heating and space heating. It includes mul- ti series collectors, and a large solar storage system. A heat exchan- ger is needed to transfer solar energy to preheat domestic hot water and to provide space heating. The system is ideally suited to allow solar heating of radiant floor systems. Of course, there is

still a requirement for a back-up heating system. Boilers are fuel- burning appliances that produce hot water that gets circulated through piping for heating uses.

A schematic diagram for the main components of the integrated energy saving system with boiler, electrical heater, solar collector and storage tanks are shown in Fig. 4.

In the present work, the schematic diagram for the designed cy- cle of the integrated energy saving system with boiler, electrical heater, solar collector, DHW, control board, digital temperature monitor, expansion tank, check and pressure relief valves, and pressure gauge, and storage tank with internal heat exchangers are shown in Fig. 5. The designed system consists of three loops, namely: the collector loop, the space heating load loop, and the domestic hot water loop.

The collector loop consists of collectors (3), storage tank (7), cir- culating pump (1), and other subsidiary components. The space heating loop includes the storage tank (7), the expansion tank (10), the load devices (under-floor heaters or fan coil units), and the back-up system (11). The system is equipped with a flow con- trol valve (4) and other supplementary components. The hot water loop includes: a storage tank (8), a heat exchanger immersed in the storage tank and a circulating pumps (1).

The liquid storage tank is best to be spherical to minimize heat losses and tank material requirements. However, spherical tanks are difficult to fabricate, consume a volume in the building which is about twice of its volume, and require special supports. A com- promise shape, easier to fabricate is a right circular cylinder with a height equal to its diameter. The surface area of such a tank is only about 15% greater than of a sphere, such a tank designed according to our requirement. The storage tank used for heat storage is of the cylindrical type (1500 L capacity).

Many differential temperature controls monitor the tempera- tures at the collector outlet and at the solar storage tank. When the collectors are hotter than the tank, the control turns on a circu- lator which circulates the fluid through the collectors and back to the heat exchanger. Heat is stored in the storage tank until it is called for. When there is draw on the domestic water system, cold water flows through a heat exchanger in the storage tank and out to an auxiliary water heater and then to the point of use. As the water is passed through the heat exchanger, it is heated to the tem- perature of the storage tank. If the water has not reached delivery temperature by the time it enters the auxiliary heater, this heater will turn on and provide supplementary heat, e.g. [21]. The most important control element in the integrated boiler–solar system is the temperature differential controller to control the operation of pumps. If the temperature sensed by a thermistor connected to the absorber plate of the solar collector, exceeds the tempera- ture in the bottom of the storage tank by a certain value (usually 5 �C), the collector pump will be activated and will continue to run until the collector and storage temperature are within 1–2 �C of each other. At this point the pump will be turned off. This con- troller is also used to protect the solar collector from freezing.

These collectors are the type being designed and manufactured by the RSS, e.g. [21]. Solar water heating is most effective when it can provide hot water under coldest conditions, i.e. winter. The col- lectors should be oriented to the south with a winter operation tilt angle of approximately 45� (13� greater than the local latitude). Piping layout should be arranged in a way that the hot water outlet piping is shorter than the supply piping to minimize heat losses.

5. Results and discussions

Selecting a building’s comfort system represents a complex tradeoff between numbers of different perspectives. Architects, engineers, contractors, building owners and developers have many

Fig. 4. A schematic diagram of the integrated solar energy saving system with boiler, electrical heater, solar collector and storage tank.

Fig. 5. A schematic diagram of the designed integrated solar energy saving system with boiler, electrical heater, solar collector and storage tank.

A. Al-Salaymeh et al. / Energy Conversion and Management 51 (2010) 1621–1628 1625

things to consider. While the heating system may represent only 10% of the building’s total cost, poor decisions in system design made today can result in significant problems for building occu- pants and owners tomorrow.

The integrated boiler–solar system uses solar energy to sub- stantially reduce energy costs. This system effectively provides en- ergy nearly free cost using the solar energy during cold and hot weather without the requirement to run a boiler. The boiler is essentially shut off during this period, thereby saving energy and

also allowing scheduled preventative maintenance to take place. The boiler can be shut down form 7 to as may as 9 months a year.

Solar energy can be used to save energy whenever the outside condition is sunny. This energy-efficiency measure can save en- ough boiler power to pay for solar collectors and storage tanks installation costs in less than 3 years. The payback period for the solar energy system is different in each case. The more hot water you use, for example with more people in the house, the more you will save by having a solar system. Also if you use more hot

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Fig. 7. Energy cost of the fuel consumption for space heating and domestic hot water at different months around the year in the case of the boiler system only.

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Fig. 8. Energy cost of the fuel consumption for space heating and domestic hot water at different months in the case of the integrated combined system.

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water in sunny weather the more you will save, because that’s when free hot water is available. The other factor is the cost of existing fuel, which may range from an efficient condensing gas boiler to an electric immersion heater.

In order to study the economic effect of using the integrated boiler–solar system on the cost of the operating of boiler in the domestic hot water and space heating, a case study has been car- ried out for small flat which has approximately 200 m2.

Most people make a purchase to solve a real or perceived prob- lem. They use economic evaluations to justify their decision. A number of factors influence the costs of owning and operating an integrated solar–boiler energy saving system. These include: Installation cost, operating costs (including all the fuel and electric costs to accommodate one alternative over others) and mainte- nance costs.

Fig. 6 shows the average values of the minimum and maximum temperatures for each month in the year at the location of Euro Company in Marka which is located between Amman and Zarka cities, e.g. Al-Salaymeh et al. [22]. It is clear from Fig. 6 shows that we can get benefits from the solar energy for space heating at many months in the year. The space heating can be used in the case, where the ambient temperature is below 19 or 20 �C.

In order to calculate the thermal performance of a solar collec- tor, we assumed the wind speed to be 3.8 m/s. The overall heat loss coefficient for the collector has been calculated. Also, the heat re- moval factor, the useful energy, the absorber plate temperature have been calculated.

For the present case study, the total amount of fuel consump- tion in winter season for both space heating and domestic hot water (300 L/day) when the conventional boiler system is used, is 4.815 m3/season. The amount of fuel consumed in summer sea- son for the domestic hot water when the boiler alone has been used is 0.3867 m3/season. However, the total amount of the fuel consumption all around the year for domestic hot water is about 0.6766 m3/year if the boiler alone is used. The current price of the fuel cost in Jordan is 0.33 JD for 1 L of diesel. The total cost of fuel in 1 year using boiler only is 314.5 JD/year. With respect to the heating space, the total amount of the fuel consumed all around the year for space heating for the case study is about 1.817 m3/year if the boiler alone is used. This quantity of fuel costs 844.5 JD/year. The energy cost of domestic hot water and space heating at different months for boiler system only is shown in Fig. 7.

Fig. 8 presents the fuel cost required for space heating and domestic hot water for the same case study, but in the case of using the integrated boiler–solar energy saving system. In the case of the integrated boiler–solar energy saving system, the total amount of

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Fig. 6. The temperature distributions for the minimum and maximum values of ambient temperature at different months for Marka city.

the fuel consumed for domestic hot water is reduced to zero in summer and to 0.2214 m3 in all around the year. Thus, the total cost of fuel for domestic hot water in 1 year using the integrated energy system is 106.4 JD/year.

The saving in energy with respect to the heating space is clearly shown in Fig. 8. The total amount of the fuel consumed all around the year for space heating is about 1.28 m3/year and this quantity of fuel costs 597.1 JD/year. The total cost of fuel consumed for the domestic hot water in our case study if the conventional boiler sys- tem is used is 314.5 JD/year. This quantity is reduced to 106.4 JD/ year in the case of using an integrated energy saving system. A comparison for the energy cost of domestic hot water between the combined integrated energy boiler–solar system and the con- ventional boiler system is shown in Fig. 9.

Fig. 10 presents similar results as shown in Fig. 11, but the com- parison between the combined integrated system and the conven- tional system is based on the energy requirement for space heating. The total cost of fuel needed for space heating is reduced from 844.5 JD/year in the case of using the conventional boiler sys- tem to 597.1 JD/year in the case of using an integrated energy sav- ing system.

The amount of fuel consumed during a whole year if the con- ventional boiler system is used for the present case study is 2.49 m3/season. The most quantity of fuel consumption is needed in winter season for space heating. About 89% from the fuel energy requirement is used in winter season which is about 2.20 m3/sea-

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Fig. 10. A comparison between the energy needed for space heating in the case of the conventional boiler system and the integrated combined system.

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Fig. 11. A comparison between the total energy requirement for domestic hot water and space heating for the conventional boiler system and the integrated system at different months.

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Fig. 12. Percentage of energy saving as a function of the time around the year in the case of using the combined integrated boiler–solar energy instead of boiler only.

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Fig. 9. A comparison between the energy demand for domestic hot water in the case of the conventional boiler system and the integrated combined system at different months.

A. Al-Salaymeh et al. / Energy Conversion and Management 51 (2010) 1621–1628 1627

son. The amount of fuel consumed in summer season for both space heating and domestic hot water in the case of the conven- tional boiler system is about 0.29 m3/season which is less than 11% from the total energy requirement.

Furthermore, the amount of fuel consumed for both space heat- ing and domestic hot water in the case of the combined integrated system is 1.5 m3/year which is 1 m3 less than the energy needed in case of the conventional energy system. The amount of fuel needed in winter season for both space heating and domestic hot water in the case of the combined integrated system is about 99% from the total required energy in the whole year. Fig. 11 shows a compari- son between the total energy cost for both space heating and domestic hot water of the two energy systems.

The percentage of energy saving system ranges from 27% at winter season to 100% at summer season as shown in Fig. 12. Of course, reducing 40% of the annual domestic hot water and space heating saves 330 JD each year of the fuel cost which is typical for families of 2–4. Larger families and larger space building save even more.

6. Conclusions

The aim of the present study was to develop and demonstrate both the technical and economical viability of a combined solar boiler integrated system that can run alternately, or simulta- neously to reduce the yearly energy bill which was increased 3 times in the last 2 years in Jordan. The feasibility of the combined solar boiler integrated system concept has been demonstrated.

The economical study about the integration system of boiler and solar energy shows that using solar water heaters to heat space and for domestic water is cost-effective. Payback can be as low as 3 years, and utility bills are much lower than they would be using a conven- tional heating system. The payback period can be slightly changed depending on the fluctuation fuel price in the world market.

With space and water heating by using a flat-plate solar collec- tor, about 39% of home energy use can be reduced. Therefore, the solar energy is an attractive method of reducing a home’s fossil fuel consumption. The under-floor heating system has a high efficiency and can be installed mainly in new buildings. However, for the existing buildings, fan coil units might be more suitable. Evacu- ated-tube is more efficient and commercial than the flat-plate solar collectors.

References

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