A Comparison of Solar Photovoltaic and Solar Thermal Collector for Residential Water Heating and Space Heating System

Almost all single-family detached house in Canada consume huge electricity for space heating and domestic hot water (DHW) purposes. There are many possibilities to design an energyefficient house. A solar water heating system can be used for domestic water and space heating. Water temperature can be kept constant always by connecting a heat pump or oil burner because solar energy is intermittent. Proper and optimized solar photovoltaic and collector design, tank design, heat pump selection, house insulation, total demand calculation in each section are essential. EnergyEfficient house design has been proposed with water heating and space heating system and compared with the existing system, solar PV based systems, and solar collector based system. The tracking and non-tracking based solar thermal collector based and the solar photovoltaic based system has been compared in this paper and investigate the suitable one for practically applicable and acceptable by the people. Simulation has been done by using the PolySun software. It found that by implementing the proposed PV based system with tracking is highly suitable considering lower cost, high output power, flexibility, easy installation.


I. INTRODUCTION
Solar PV installation in Canada is rapidly growing. Currently, the residential and commercial solar breakeven is comparatively much less than the grid electricity prices, for example, the solar energy cost is 6.8 cents/kWh average whereas the grid electricity price is 12 cents/kWh [1]. It is assumed that the rooftop PV or collector panel could mitigate about half of Canada's residential energy requirement [2]. The price of PV technology has significantly decreased over the last few decades, and the efficiency of the PV panel increased. Some manufacturers demanded that efficiency is around 23% [3]. Among all methods of power generation in Canada, solar energy is contributing more than 1%, and the total generation is more than 3000 MW [4]. This heat energy can be used to provide domestic hot water (DHW) supply, and space heating purposes as almost all Canadian single-family houses are using electricity for both.
Thermal energy storage (TES) system is a structure to store thermal energy for space heating and domestic hot water supply in different mediums such as water, latent heat, sensible heat, and many more [5] [6]. Because of several advantages nowadays, the active control of the integrated system with photovoltaic thermal (PVT) is used to a large extent to reduce the energy mismatch between supply and demand through a controller [7]. Canada's Energy Future Published on December 6, 2019 Authors are with Memorial University of Newfoundland, Canada.
(2018) published a report and mentioned that the present per capita greenhouse emission (GHG) is around 22 %. Considering its reduction planning to reduce it to below 5% by 2030 [8]. Based on the Government of Canada, the solar contribution will increase to around 5% by 2025, which will significantly help to reduce the CHG emission [9].

II. LITERATURE REVIEW
Renewable energy sources provide more than 17% of Canada's total primary energy supply currently [10]. Lots of research is conducted on solar thermal energy storage systems with renewable sources. M. Ghorab et al. [11] verified that the solar fraction, as well as output, would increase proportionally with the increase of the solar collector area.
They also suggested that hybrid residential energy enduse and emissions model is beneficial to make an efficient detached house. M. C. Rodríguez-Hidalgo et al. [12] investigated in his research that for the long-term performance, the TES systems with multisource heat pump, and solar collectors are efficient, and cheapest way to produce heat for space heating. S.Z. Mozabieh et al. [13] highlighted that the cumulative lifecycle energy and carbon analysis, as well as energy payback periods and net energy ratios, are also crucial for making an energy-efficient house.
A single-family house can make energy-efficient, even net-zero carbon emission by using an all-electric solution. J. L. Garcia et al. [14] mentioned that the solar collector based DHW system performance depends on water flow rate, draw time and duration, city water temperature, control of water circulation loop, and system layout. From their experiments, they found that most of the collected energy goes to the loads. They used a concentrating solar collector and rockbed storage with air as a working medium for a long-term house heating system. The authors [11] suggested making an energy-efficient house by improving the house design parameters such as walls, insulation, windows, ceiling fan, and so on.
Some Universities in Canada are doing some research related to the sessional energy storage systems. For instance, the University of Ontario Institute of Technology built a low-temperature borehole thermal energy storage system (BTES) in 1990, which had 384 holes, provide the basis for a highly efficient heating and cooling system for eight University buildings [15], [16].
In the Drake Landing Solar Community (DLSC) project [17] in 2007, which is supplying 90% of heat demand and 60% hot water demand in total 52 numbers of single house In this work, a thermal energy storage system with a necessary control system has been designed for a singlefamily residential house. Finally, the performance and installation costs of both systems have been compared.

III. DATA COLLECTION AND ANALYSIS
A. Weather Analysis The tested house location is 5, Blue River Place, St. John's, NL, Canada. Based on the PolySun software analysis, the minimum wind speed for power generation is 2m/s, and the maximum value is 10 m/s. The average daily solar radiation is 3.06 kWh per m2 per day, which is enough to generate heat or electricity.

B. House Analysis
The considered house is a typical single-family house in Canada, and the details of this house are described in Table  I. In the tested house, the hot water supplied by an electric boiler and space heating is provided by the grid electricity. Thus the vast grid electricity is required, and consumers are paying a large number of electric bills every year. Based on NL power annual bill summary, the considered house present annual demand is around 19007 kWh of electricity for space heating, DHW, and other electrical appliances, as shown in Fig. 1. The distribution of this consumption shown in Fig. 2 where it is shown that most of the electricity consumed for space heating and DHW.

C. House Analysis in BEopt Software
This house again was analyzed by using the BEopt Software. All input parameters have been selected carefully based on the existing house materials. The simulation output is shown in Fig. 3.  It is a result that the actual energy consumption in the house in Fig. 1 is almost like the electrical and thermal consumption of the house, as shown in Fig. 3.

IV. SOLAR COLLECTOR BASED SYSTEMS
Currently, the house is just a typical single-family house. All energy demand is provided form the grid electricity. To modify it, a solar thermal collector relates to two water tanks. As solar energy is always variable, the preheating tank water temperature may always not reach the desired value. That is why an auxiliary burner is added with the main tank that will help to keep the water temperature at the desired level. The modified space heating and hot water supply diagram in a single-family house given in Fig. 4

A. Design of Solar Collector
In this research, the water medium is considered in the tanks. The stored hot water carried to the radiator for space heating purposes and to the hot water taps (kitchen, Where ηk is the collector efficiency and η_sys is system efficiency. If 100% solar fraction, the maximum value considered then, Collector array, CA=Q/CY =(6.89 kWh)/(1.392 kWh/m 2 ) = 4.95 m2 The design calculation for space heating given below: A standard flat plate collector can produce 9085.23 kW/m 2 /day [18], and the daily requirement is 202.7 kW/m 2 /day The required number of collectors= (Daily requirement)/(Collector output)=0.0223 (m 2 /day) (5) The total number of collectors=0.02231(m 2 /day) × 125.27 m 2 =2.7 per day.

B. Installation cost analysis
The setup cost distribution for the solar collector and energy storage system described in Fig. 6. Fig. 6. Installation cost distribution by section [18] The calculation has been done based on the above design and the latest market price according to Amazon.ca. It is found that the total investment cost with oil burner is CA $53,600 and with heat pump is CA $54,600.

C. Simulation Result
The modified single-family house, as shown in Fig. 4 has been designed and simulated in a professional PolySun designer environment. In this simulation, there are two models considered, for example, model 1: a collector, an oil burner for heat sources, and model 2: a collector, heat pump for heat sources. The system other parts remain the same for both cases. The simulation was done carefully for every month of a year. The collector output is available around the year, as shown in Fig.7. The average efficiency of the oil burner is 95% and the heat pump efficiency is 300% to 500%. Usually, from Jun to Aug is the hottest months in NL, Canada, so the overall demand is lower than the other months, as shown in Fig. 8. The performance of both systems is compared in Table II. In NL, Canada, the electricity price is 0.12 CAD/kWh that considered for electric bill calculation. Usually, one liter of furnace oil price is 0.82 CAD, which is also equivalent to 10.27 kWh of energy is also considered in the calculation.

V. SOLAR PV BASED SYSTEMS
The central systems in Fig. 4 is considered again with the solar PV module instead of solar thermal collector, and the design steps are given below [19]:

C. Control and Monitoring Systems
The complete system is shown in Fig. 8, and the controller operating principle is described in Fig. 9. During the day time, when the sunshine is available, the threeposition switch transfers the AC power to the water tank. The sensors always monitor the water temperature; when reaching the tree position switch, transfer the power to the room heater-1 and room heater-2. After consumption of some hot water, new cold water comes into the tank; if the temperature is below the set temperature, the three-position switch again connects to the tank. In this way, the water tank temperature always maintains the set temperature. During the night time, auxiliary heater coil supplies heat from the electric grid to the water to maintain the water temperature based on the set temperature. When the water level goes to the desired level, then valve two is not taking cold water. Similarly, when the level goes lower than valve two opens until the tank fills up. The controller will do everything, as shown in Fig. 9.

D. Calculation of the Investment Cost
The whole system is designed and described in section 5.1~5.2. There are factors associated with the installation cost. The percentage of cost distribution, as shown in Fig.10 [22]. The calculation and the total installation cost has been done based on the above design and the latest market price according to Amazon.ca and it is calculated that the total implementation cost will be CA $22,350.

E. Simulation Result
The total solar PV based space and water heating system is described in Fig. 8. This complete system has been designed and simulated in the PolySun software environment. The total output of all PV modules shown in Fig. 11 and the house consumption is shown in Fig. 12. It is investigated that it varies month to month but not more than 600 kWh per month that will mitigate from the batteries when sunshine is not available.

VI. OVERALL COMPARISON OF BOTH SYSTEMS
Comparing the design, sizing, cost analysis, output power, rate of return of both systems, and the final overview has been summarized in Table III.
Every year, the depreciation cost has been considered as 5% of the investment and calculated the total annual savings up to 30 years, as shown in Fig. 13 where the annual savings comparison for both systems is shown for 30 years. Fig. 13. The annual savings comparison The PV based system is much cheaper than solar thermal collectors-based systems. The PV based system needs lower maintenance and longer lifetime as well.

VII. CONCLUSION
By implementing, the solar collector based thermal energy storage system, it is possible to save 50% of electricity and by solar photovoltaic based system, it is possible to save 100% of electricity for residential purposes. From the above design and calculations, it is concluded that the setup cost of a solar collector-based system is higher compared to the PV based system, but the output power is much lower in solar collector-based system. This system is also suitable for other house appliances as well. In the selected house rooftop, space is two times space available compared to the required space, or usually, all Canadian single-family residential houses have this space. Finally, in overall justification, the solar PV based system is a more suitable, cost-effective, and reliable solution for house appliances, water heating, and space heating purposes. This system can be further designed and simulated with solar combi system with another type of control system.