public void setAverageDailyHoursOfSunlight(Double input) throws SolarPowerSystemException {
		if (input < 0.0 || input > 24.0) {
			throw new SolarPowerSystemException("Dverage daily hours of sun light " +
												"should be between 0 and 24 hours."); 
		} else {
			this.averageDailyHoursOfSunlight = input;
		}
	}