Hydro Load AssessmentHydro Load AssessmentHow do you know how How do you know how much energy you need?much energy you need?– Electric billElectric bill– Average US household Average US household

uses 850 kWhrs/month = 28 uses 850 kWhrs/month = 28 kWhrs/daykWhrs/day

– Also need Also need capacitycapacity: what is : what is the largest load to run?the largest load to run?

– Do a load assessment!!Do a load assessment!!

Load AssessmentLoad AssessmentA house on RE must use less electricityA house on RE must use less electricity– Use less energy! produce the Negawatt!Use less energy! produce the Negawatt!– Efficient appliancesEfficient appliances

CF lightingCF lighting

Newer models (EnergyStar)Newer models (EnergyStar)

– Divert heating loads to solar, gas, etc…Divert heating loads to solar, gas, etc…

Frugal Lighting RuleFrugal Lighting Rule

One light per personOne light per person

One light for the roomOne light for the room

Task lighting is good for the eyes

Load AssessmentLoad AssessmentYou’ll need for each appliance…You’ll need for each appliance…– Power consumptionPower consumption

In WattsIn Watts

Rating will be stamped on applianceRating will be stamped on appliance

– Number of hours/day appliance is onNumber of hours/day appliance is on

Simple example: a 15 W CF bulb is on for an Simple example: a 15 W CF bulb is on for an average of 5 hrs/dayaverage of 5 hrs/day

day: (15 W)(5 hrs/day) = 75 Whrs/dayday: (15 W)(5 hrs/day) = 75 Whrs/day

month: (75 Whrs/day)(30 days) = 2,250 Whrsmonth: (75 Whrs/day)(30 days) = 2,250 Whrs

= 2.25 kWhrs= 2.25 kWhrs

Load AssessmentLoad AssessmentSome special casesSome special cases– Cycling loadsCycling loads

Most heating appliances are on a thermostat – not on Most heating appliances are on a thermostat – not on 24/7 (space heating, fridge, water heater, etc)24/7 (space heating, fridge, water heater, etc)

– Surge requirementSurge requirementMotors requires additional current when startingMotors requires additional current when startingRule of thumb: starting power = 3 times rated powerRule of thumb: starting power = 3 times rated powerImportant for “large discharge current at C/10”Important for “large discharge current at C/10”

– Phantom loadsPhantom loadsMany appliances consume power even when off Many appliances consume power even when off (24/7)(24/7)

– TimersTimers– TransformersTransformers

Load AssessmentLoad AssessmentPotential errors?Potential errors?– Usage changes with seasonUsage changes with season– Appliance efficiency often decreases with ageAppliance efficiency often decreases with age– Most “duty cycles” must be measured Most “duty cycles” must be measured

Load AssessmentLoad AssessmentExample: summer cabinExample: summer cabin– Loads: Loads:

Lights: all 15 W CF, on a total of 10 hrs/dayLights: all 15 W CF, on a total of 10 hrs/day

Radio: on 2 hrs/day (20 W)Radio: on 2 hrs/day (20 W)

TV: on 2 hrs/day (40 W)TV: on 2 hrs/day (40 W)

Small fridge: on 8 hrs/day {you measured it} (400 W)Small fridge: on 8 hrs/day {you measured it} (400 W)

Water pump: on 2 hrs/day {fills cistern} (500 W)Water pump: on 2 hrs/day {fills cistern} (500 W)

– Other loads diverted to propaneOther loads diverted to propane

Load AssessmentLoad AssessmentAverage daily usageAverage daily usage– Lights: (15 W)(10 hrs/day) = 150 Whrs/dayLights: (15 W)(10 hrs/day) = 150 Whrs/day– Radio: (20 W)(2 hrs/day) = 40 Whrs/dayRadio: (20 W)(2 hrs/day) = 40 Whrs/day– TV: (40 W)(2 hrs/day) = 80 Whrs/dayTV: (40 W)(2 hrs/day) = 80 Whrs/day– Small fridge: (400 W)(8 hrs/day) = 3200 Whrs/dSmall fridge: (400 W)(8 hrs/day) = 3200 Whrs/d– Water pump: (500 W)(2 hrs/day) = 1000 Whrs/dWater pump: (500 W)(2 hrs/day) = 1000 Whrs/d– TOTAL: 4510 Whrs/day = 4.5 kWhrs/dayTOTAL: 4510 Whrs/day = 4.5 kWhrs/day– Assume all 120 V loadsAssume all 120 V loads

Hydro SizingHydro Sizing

Energy required = 4.5 kWhrs/dayEnergy required = 4.5 kWhrs/dayOr (4.5 kWhrs/day)(30days/month) = 135 Or (4.5 kWhrs/day)(30days/month) = 135 kWhrs/monthkWhrs/monthHydro Power = (135 kWh/mo)(1mon/720h) Hydro Power = (135 kWh/mo)(1mon/720h) = .188 kW or 188W= .188 kW or 188WSo, we need a hydro system producing at So, we need a hydro system producing at least 188W all the time.least 188W all the time.Say we have 50’ of head, we’ll need to use Say we have 50’ of head, we’ll need to use at least 38 GPM of flowat least 38 GPM of flow

Battery Bank SizingBattery Bank SizingBattery storage for PV and Wind systems Battery storage for PV and Wind systems typically require 3 or more days of battery typically require 3 or more days of battery storagestorage

Hydro systems run all the timeHydro systems run all the time

Batteries in a hydro system typically need to Batteries in a hydro system typically need to store energy for less than a daystore energy for less than a day

Often, the battery is sized to provide Often, the battery is sized to provide sufficient current to the inverter rather than sufficient current to the inverter rather than an amount of storage (at the C/10 max rate)an amount of storage (at the C/10 max rate)

Battery SizingBattery SizingAverage daily usage = 4510 Whrs/dayAverage daily usage = 4510 Whrs/day

Size of battery bank needed?Size of battery bank needed?– Must choose system voltage! Must choose system voltage!

Usually 12, 24, 48VDCUsually 12, 24, 48VDC

– Choose 48 VChoose 48 V– 4510 Whrs/day / 48 V = 94 Ahrs/day4510 Whrs/day / 48 V = 94 Ahrs/day

Battery Bank SizingBattery Bank SizingStorage needed: 94 Ahrs/day at 48 VStorage needed: 94 Ahrs/day at 48 V

Inverter efficiency: 94 Ahrs/d/0.9 = 104 Ahrs/dInverter efficiency: 94 Ahrs/d/0.9 = 104 Ahrs/d

1 day res.: (104 Ahrs/day)(1 d) = 104 Ahrs1 day res.: (104 Ahrs/day)(1 d) = 104 Ahrs

Temp penalty at 60Temp penalty at 60°F: (104 Ahrs)(1.11) = 116 Ahrs°F: (104 Ahrs)(1.11) = 116 Ahrs

Leave a 20% reserve: (116 Ahrs)(1.20) = 139 AhrsLeave a 20% reserve: (116 Ahrs)(1.20) = 139 Ahrs

Choose 220 Ahrs, 6 V batteries: need a 48 V Choose 220 Ahrs, 6 V batteries: need a 48 V batterybattery

The 48 V battery will need (8) 6 V batteries in The 48 V battery will need (8) 6 V batteries in seriesseries

Total = 8 batteries, 48V, 220 AhrsTotal = 8 batteries, 48V, 220 Ahrs

Battery Bank SizingBattery Bank SizingShould pump and fridge run at the same Should pump and fridge run at the same

time?time?

Max discharge rate = C/10Max discharge rate = C/10

C/10 = 220 Ahrs/10 hrs = 22 AC/10 = 220 Ahrs/10 hrs = 22 A

Pump + fridge = 900 W/48 V = 19 APump + fridge = 900 W/48 V = 19 A

Should be able to handle this possible surgeShould be able to handle this possible surge

Check the charge rateCheck the charge rate

We can charge the battery at a max rate of C/10 We can charge the battery at a max rate of C/10 or 22Aor 22AIf we end up with a 250W hydro system at 48V, If we end up with a 250W hydro system at 48V, the current will be 250W/48V = 5.2A, no the current will be 250W/48V = 5.2A, no problem, nice and slowproblem, nice and slowAt this charge rate, it would take 220Ah/5.2A = At this charge rate, it would take 220Ah/5.2A = 42 hours to charge or C/4242 hours to charge or C/42Sounds slow, but we will typically only partially Sounds slow, but we will typically only partially drain the batteries, say 20%.drain the batteries, say 20%.(.2)(220Ah)=44Ah removed during the day(.2)(220Ah)=44Ah removed during the dayAt 5.2A, it would take 44Ah/5.2A=8.5 hours to At 5.2A, it would take 44Ah/5.2A=8.5 hours to charge back (overnight)charge back (overnight)

Davis Rating ScaleDavis Rating Scale

1.1. BasicsBasics

2.2. EssentialsEssentials

3.3. Modern ConveniencesModern Conveniences

4.4. Hot Water HeatHot Water Heat

5.5. Space HeatingSpace Heating

6.6. Full Service HouseholdFull Service Household

1. Basics1. Basics

Lighting, weekend cabin, Lighting, weekend cabin, small RVsmall RV

A small PV system may be A small PV system may be the most appropriatethe most appropriate

50 to 250W inverter50 to 250W inverter

If you need power in the If you need power in the winter, nano-hydro may winter, nano-hydro may outperform PVoutperform PV

2. Essentials2. Essentials

““Lights and Music”Lights and Music”

Lights, small appliances like stereo, Lights, small appliances like stereo, blender, laptopblender, laptop

35 to 70 kWhrs/month35 to 70 kWhrs/month

50 to 100W hydro system50 to 100W hydro system

300 to 1000W inverter300 to 1000W inverter

3. Modern Conveniences3. Modern Conveniences

Lights, stereo, blender, laptop, refrigeration, Lights, stereo, blender, laptop, refrigeration, freezing, water pumping….everything that freezing, water pumping….everything that doesn’t require much heatdoesn’t require much heat

75 to 125 kWhrs/month with efficient appliances75 to 125 kWhrs/month with efficient appliances

100 to 200W hydro system100 to 200W hydro system

Need a sufficient inverter capacity for max loadsNeed a sufficient inverter capacity for max loads

An “easy start kit” can reduce starting surgeAn “easy start kit” can reduce starting surge

A nice 2.5 to 4kW true sine wave inverter should A nice 2.5 to 4kW true sine wave inverter should do itdo it

4. Hot Water Heating4. Hot Water Heating

Will require an AC system, lots of waterWill require an AC system, lots of waterBatteries and large heating loads don’t mixBatteries and large heating loads don’t mixRecovery time may be slow (3412 BTUs Recovery time may be slow (3412 BTUs per kW), hot water heaters usually have per kW), hot water heaters usually have two 4500W elements for fast reheattwo 4500W elements for fast reheatMore efficient to use solar or low-grade More efficient to use solar or low-grade energy for heating waterenergy for heating waterHigh grade energy: electricityHigh grade energy: electricityLow grade energy: gasLow grade energy: gas

5. Space Heating5. Space Heating

Will require a full sized AC systemWill require a full sized AC system

1000 to 2000 kWhrs/month1000 to 2000 kWhrs/month

1 continuous kW heats a little better than a 1 continuous kW heats a little better than a cord of firewoodcord of firewood

For a six month heating season, a 10kW For a six month heating season, a 10kW hydro system = 12 cords of firewoodhydro system = 12 cords of firewood

6. Full Service Household6. Full Service Household

More power than you know what to do withMore power than you know what to do with

High current appliances (ranges and High current appliances (ranges and dryers)dryers)

Usually a surplus of power which can be Usually a surplus of power which can be sold $$$$$$$$$$$$sold $$$$$$$$$$$$

Many thousands of kWhrs/monthMany thousands of kWhrs/month